Visual Evoked Potential and Magnetic Resonance Imaging are More Effective Markers of Multiple Sclerosis Progression than Laser Polarimetry with Variable Corneal Compensation.

PubMed

Kantorová, Ema; Ziak, Peter; Kurča, Egon; Koyšová, Mária; Hladká, Mária; Zeleňák, Kamil; Michalik, Jozef

2014-01-01

The aim of our study was to assess the role of laser polarimetry and visual evoked potentials (VEP) as potential biomarkers of disease progression in multiple sclerosis (MS). A total of 41 patients with MS (82 eyes) and 22 age-related healthy volunteers (44 eyes) completed the study. MS patients were divided into two groups, one (ON) with a history of optic neuritis (17 patients, 34 eyes) and another group (NON) without it (24 patients, 48 eyes). The MS patients and controls underwent laser polarimetry (GDx) examination of the retinal nerve fiber layer (RNFL). In the MS group, we also examined: Kurtzke "expanded disability status scale" (EDSS), the duration of the disorder, VEP - latency and amplitude, and conventional brain magnetic resonance imaging (MRI). Our results were statistically analyzed using ANOVA, Mann-Whitney, and Spearman correlation analyses. In the MS group, brain atrophy and new T2 brain lesions in MRI correlated with both VEP latencies and amplitudes. Separate comparisons revealed VEP latency testing to be less sensitive in ON than in NON-patients. In ON patients, VEP amplitudes correlated mildly with brain atrophy (r = -0.15) and strongly with brain new MRI lesions (r = -0.8). In NON-patients, highly significant correlation of new MRI brain lesions with VEP latencies (r = 0.63, r = 0.6) and amplitudes (r = -0.3, r = -4.2) was found. EDSS also correlated with brain atrophy in this group (r = 0.5). Our study did not find a correlation of GDx measures with MRI tests. The GDx method was not able to detect whole brain demyelinization and the degeneration process, but was only able to reveal the involvement of optic nerves in ON and NON-patients. In our study, we found that both methods (VEP and GDx) can be used for the detection of optic nerve damage, but VEP was found to be superior in evaluating whole brain demyelinization and axonal degeneration. Both VEP and MRI, but not GDx, have an important role in monitoring disease progression in MS patients, independent of the ON history.

Visual evoked potentials of mildly mentally retarded and control children.

PubMed

Gasser, T; Pietz, J; Schellberg, D; Köhler, W

1988-10-01

Visual evoked potentials (VEPs) were recorded from 25 10- to 13-year-old mildly mentally retarded children and compared with those from 31 control children of the same age-range. Correlations of VEPs with age were weak, but a relationship between VEPs and IQ was demonstrated for the control group. The retarded group had significantly longer latencies and higher amplitude peaks than the control group, with the differences occurring primarily over non-specific cortex and for secondary components. Analysis also showed that the retarded group were neurophysiologically heterogeneous. Since the same children had been analyzed earlier by quantitative EEG methods, comparisons are made with respect to these two methods of investigating brain function.

Multifocal visual evoked potential in optic neuritis, ischemic optic neuropathy and compressive optic neuropathy

PubMed Central

Jayaraman, Manju; Gandhi, Rashmin Anilkumar; Ravi, Priya; Sen, Parveen

2014-01-01

Purpose: To investigate the effect of optic neuritis (ON), ischemic optic neuropathy (ION) and compressive optic neuropathy (CON) on multifocal visual evoked potential (mfVEP) amplitudes and latencies, and to compare the parameters among three optic nerve disorders. Materials and Methods: mfVEP was recorded for 71 eyes of controls and 48 eyes of optic nerve disorders with subgroups of optic neuritis (ON, n = 21 eyes), ischemic optic neuropathy (ION, n = 14 eyes), and compressive optic neuropathy (CON, n = 13 eyes). The size of defect in mfVEP amplitude probability plots and relative latency plots were analyzed. The pattern of the defect in amplitude probability plot was classified according to the visual field profile of optic neuritis treatment trail (ONTT). Results: Median of mfVEP amplitude (log SNR) averaged across 60 sectors were reduced in ON (0.17 (0.13-0.33)), ION (0.14 (0.12-0.21)) and CON (0.21 (0.14-0.30)) when compared to controls. The median mfVEP relative latencies compared to controls were significantly prolonged in ON and CON group of 10.53 (2.62-15.50) ms and 5.73 (2.67-14.14) ms respectively compared to ION group (2.06 (-4.09-13.02)). The common mfVEP amplitude defects observed in probability plots were diffuse pattern in ON, inferior altitudinal defect in ION and temporal hemianopia in CON eyes. Conclusions: Optic nerve disorders cause reduction in mfVEP amplitudes. The extent of delayed latency noted in ischemic optic neuropathy was significantly lesser compared to subjects with optic neuritis and compressive optic neuropathy. mfVEP amplitudes can be used to objectively assess the topography of the visual field defect. PMID:24088641

Fractal Dimension Analysis of Transient Visual Evoked Potentials: Optimisation and Applications.

PubMed

Boon, Mei Ying; Henry, Bruce Ian; Chu, Byoung Sun; Basahi, Nour; Suttle, Catherine May; Luu, Chi; Leung, Harry; Hing, Stephen

2016-01-01

The visual evoked potential (VEP) provides a time series signal response to an external visual stimulus at the location of the visual cortex. The major VEP signal components, peak latency and amplitude, may be affected by disease processes. Additionally, the VEP contains fine detailed and non-periodic structure, of presently unclear relevance to normal function, which may be quantified using the fractal dimension. The purpose of this study is to provide a systematic investigation of the key parameters in the measurement of the fractal dimension of VEPs, to develop an optimal analysis protocol for application. VEP time series were mathematically transformed using delay time, τ, and embedding dimension, m, parameters. The fractal dimension of the transformed data was obtained from a scaling analysis based on straight line fits to the numbers of pairs of points with separation less than r versus log(r) in the transformed space. Optimal τ, m, and scaling analysis were obtained by comparing the consistency of results using different sampling frequencies. The optimised method was then piloted on samples of normal and abnormal VEPs. Consistent fractal dimension estimates were obtained using τ = 4 ms, designating the fractal dimension = D2 of the time series based on embedding dimension m = 7 (for 3606 Hz and 5000 Hz), m = 6 (for 1803 Hz) and m = 5 (for 1000Hz), and estimating D2 for each embedding dimension as the steepest slope of the linear scaling region in the plot of log(C(r)) vs log(r) provided the scaling region occurred within the middle third of the plot. Piloting revealed that fractal dimensions were higher from the sampled abnormal than normal achromatic VEPs in adults (p = 0.02). Variances of fractal dimension were higher from the abnormal than normal chromatic VEPs in children (p = 0.01). A useful analysis protocol to assess the fractal dimension of transformed VEPs has been developed.

Paired-pulse flash-visual evoked potentials: new methods revive an old test.

PubMed

Cantello, Roberto; Strigaro, Gionata; Prandi, Paolo; Varrasi, Claudia; Mula, Marco; Monaco, Francesco

2011-08-01

We aimed at reviving with modern technology the paired flash-visual evoked potential (F-VEP) testing of the visual system excitability. In the 1960s, methodological problems hindered this test, which was expected to provide important physiologic information. We studied 22 consenting healthy subjects (10 men). We recorded F-VEPs from electrodes over occipital and central brain regions. We delivered single flashes, mixed at random to flash pairs at the interstimulus interval (ISI) of 333, 125, 62.5, 50, 33, and 16.5 ms, (i.e. an internal frequency (IF) of 3, 8, 16, 20, 30, and 60 Hz). Recordings were performed with the subject's eyes closed and opened. The F-VEP was split into a "main complex" and an "afterdischarge", which we analyzed statistically in relation to the eye state (closed or open) and to the changes due to paired stimulation. The eye state affected the single F-VEP size, latency and shape significantly (p<0.05). On paired stimulation, the test (second) F-VEP exhibited significant (p<0.05), ISI-dependent size changes, such as a progressive decrease for ISIs from 62.5 to 16.5 ms (IFs of 16-60 Hz), whose timing/amount varied significantly (p<0.05) according to the eye state and to the F-VEP epoch considered. Suppression of the test F-VEP was never complete, even for the shortest ISI (ISI=16.5 ms, IF=60 Hz). The eye state (closed or open) must be considered meticulously when studying F-VEPs. F-VEP changes on paired stimulation express neural inhibition within the visual system, which can be depicted as ISI-dependent curves. Modern equipment and simplified measures render this an easy test, with statistical validity, providing specific information on the excitability properties of the visual system. Copyright © 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Chirp-modulated visual evoked potential as a generalization of steady state visual evoked potential

NASA Astrophysics Data System (ADS)

Tu, Tao; Xin, Yi; Gao, Xiaorong; Gao, Shangkai

2012-02-01

Visual evoked potentials (VEPs) are of great concern in cognitive and clinical neuroscience as well as in the recent research field of brain-computer interfaces (BCIs). In this study, a chirp-modulated stimulation was employed to serve as a novel type of visual stimulus. Based on our empirical study, the chirp stimuli visual evoked potential (Chirp-VEP) preserved frequency features of the chirp stimulus analogous to the steady state evoked potential (SSVEP), and therefore it can be regarded as a generalization of SSVEP. Specifically, we first investigated the characteristics of the Chirp-VEP in the time-frequency domain and the fractional domain via fractional Fourier transform. We also proposed a group delay technique to derive the apparent latency from Chirp-VEP. Results on EEG data showed that our approach outperformed the traditional SSVEP-based method in efficiency and ease of apparent latency estimation. For the recruited six subjects, the average apparent latencies ranged from 100 to 130 ms. Finally, we implemented a BCI system with six targets to validate the feasibility of Chirp-VEP as a potential candidate in the field of BCIs.

Face-Evoked Steady-State Visual Potentials: Effects of Presentation Rate and Face Inversion

PubMed Central

Gruss, L. Forest; Wieser, Matthias J.; Schweinberger, Stefan R.; Keil, Andreas

2012-01-01

Face processing can be explored using electrophysiological methods. Research with event-related potentials has demonstrated the so-called face inversion effect, in which the N170 component is enhanced in amplitude and latency to inverted, compared to upright, faces. The present study explored the extent to which repetitive lower-level visual cortical engagement, reflected in flicker steady-state visual evoked potentials (ssVEPs), shows similar amplitude enhancement to face inversion. We also asked if inversion-related ssVEP modulation would be dependent on the stimulation rate at which upright and inverted faces were flickered. To this end, multiple tagging frequencies were used (5, 10, 15, and 20 Hz) across two studies (n = 21, n = 18). Results showed that amplitude enhancement of the ssVEP for inverted faces was found solely at higher stimulation frequencies (15 and 20 Hz). By contrast, lower frequency ssVEPs did not show this inversion effect. These findings suggest that stimulation frequency affects the sensitivity of ssVEPs to face inversion. PMID:23205009

A Cytotoxic Type III Secretion Effector of Vibrio parahaemolyticus Targets Vacuolar H+-ATPase Subunit c and Ruptures Host Cell Lysosomes

PubMed Central

Matsuda, Shigeaki; Okada, Natsumi; Kodama, Toshio; Honda, Takeshi; Iida, Tetsuya

2012-01-01

Vibrio parahaemolyticus is one of the human pathogenic vibrios. During the infection of mammalian cells, this pathogen exhibits cytotoxicity that is dependent on its type III secretion system (T3SS1). VepA, an effector protein secreted via the T3SS1, plays a major role in the T3SS1-dependent cytotoxicity of V. parahaemolyticus. However, the mechanism by which VepA is involved in T3SS1-dependent cytotoxicity is unknown. Here, we found that protein transfection of VepA into HeLa cells resulted in cell death, indicating that VepA alone is cytotoxic. The ectopic expression of VepA in yeast Saccharomyces cerevisiae interferes with yeast growth, indicating that VepA is also toxic in yeast. A yeast genome-wide screen identified the yeast gene VMA3 as essential for the growth inhibition of yeast by VepA. Although VMA3 encodes subunit c of the vacuolar H+-ATPase (V-ATPase), the toxicity of VepA was independent of the function of V-ATPases. In HeLa cells, knockdown of V-ATPase subunit c decreased VepA-mediated cytotoxicity. We also demonstrated that VepA interacted with V-ATPase subunit c, whereas a carboxyl-terminally truncated mutant of VepA (VepAΔC), which does not show toxicity, did not. During infection, lysosomal contents leaked into the cytosol, revealing that lysosomal membrane permeabilization occurred prior to cell lysis. In a cell-free system, VepA was sufficient to induce the release of cathepsin D from isolated lysosomes. Therefore, our data suggest that the bacterial effector VepA targets subunit c of V-ATPase and induces the rupture of host cell lysosomes and subsequent cell death. PMID:22829766

Can somatosensory and visual evoked potentials predict neurological outcome during targeted temperature management in post cardiac arrest patients?

PubMed

Choi, Seung Pill; Park, Kyu Nam; Wee, Jung Hee; Park, Jeong Ho; Youn, Chun Song; Kim, Han Joon; Oh, Sang Hoon; Oh, Yoon Sang; Kim, Soo Hyun; Oh, Joo Suk

2017-10-01

In cardiac arrest patients treated with targeted temperature management (TTM), it is not certain if somatosensory evoked potentials (SEPs) and visual evoked potentials (VEPs) can predict neurological outcomes during TTM. The aim of this study was to investigate the prognostic value of SEPs and VEPs during TTM and after rewarming. This retrospective cohort study included comatose patients resuscitated from cardiac arrest and treated with TTM between March 2007 and July 2015. SEPs and VEPs were recorded during TTM and after rewarming in these patients. Neurological outcome was assessed at discharge by the Cerebral Performance Category (CPC) Scale. In total, 115 patients were included. A total of 175 SEPs and 150 VEPs were performed. Five SEPs during treated with TTM and nine SEPs after rewarming were excluded from outcome prediction by SEPs due to an indeterminable N20 response because of technical error. Using 80 SEPs and 85 VEPs during treated with TTM, absent SEPs yielded a sensitivity of 58% and a specificity of 100% for poor outcome (CPC 3-5), and absent VEPs predicted poor neurological outcome with a sensitivity of 44% and a specificity of 96%. The AUC of combination of SEPs and VEPs was superior to either test alone (0.788 for absent SEPs and 0.713 for absent VEPs compared with 0.838 for the combination). After rewarming, absent SEPs and absent VEPs predicted poor neurological outcome with a specificity of 100%. When SEPs and VEPs were combined, VEPs slightly increased the prognostic accuracy of SEPs alone. Although one patient with absent VEP during treated with TTM had a good neurological outcome, none of the patients with good neurological outcome had an absent VEP after rewarming. Absent SEPs could predict poor neurological outcome during TTM as well as after rewarming. Absent VEPs may predict poor neurological outcome in both periods and VEPs may provide additional prognostic value in outcome prediction. Copyright © 2017 Elsevier B.V. All rights reserved.

Temporal resolution of orientation-defined texture segregation: a VEP study.

PubMed

Lachapelle, Julie; McKerral, Michelle; Jauffret, Colin; Bach, Michael

2008-09-01

Orientation is one of the visual dimensions that subserve figure-ground discrimination. A spatial gradient in orientation leads to "texture segregation", which is thought to be concurrent parallel processing across the visual field, without scanning. In the visual-evoked potential (VEP) a component can be isolated which is related to texture segregation ("tsVEP"). Our objective was to evaluate the temporal frequency dependence of the tsVEP to compare processing speed of low-level features (e.g., orientation, using the VEP, here denoted llVEP) with texture segregation because of a recent literature controversy in that regard. Visual-evoked potentials (VEPs) were recorded in seven normal adults. Oriented line segments of 0.1 degrees x 0.8 degrees at 100% contrast were presented in four different arrangements: either oriented in parallel for two homogeneous stimuli (from which were obtained the low-level VEP (llVEP)) or with a 90 degrees orientation gradient for two textured ones (from which were obtained the texture VEP). The orientation texture condition was presented at eight different temporal frequencies ranging from 7.5 to 45 Hz. Fourier analysis was used to isolate low-level components at the pattern-change frequency and texture-segregation components at half that frequency. For all subjects, there was lower high-cutoff frequency for tsVEP than for llVEPs, on average 12 Hz vs. 17 Hz (P = 0.017). The results suggest that the processing of feature gradients to extract texture segregation requires additional processing time, resulting in a lower fusion frequency.

Correlation of pattern reversal visual evoked potential parameters with the pattern standard deviation in primary open angle glaucoma.

PubMed

Kothari, Ruchi; Bokariya, Pradeep; Singh, Ramji; Singh, Smita; Narang, Purvasha

2014-01-01

To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation (PSD) of Humphrey visual field could be associated with visual evoked potential (VEP) parameters of patients having primary open angle glaucoma (POAG). Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential (PRVEP) were assessed in 100 patients with POAG. The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated (full field) and displayed on VEP monitor (colour 14″) by an electronic pattern regenerator inbuilt in an evoked potential recorder (RMS EMG EP MARK II). The results of our study indicate that there is a highly significant (P<0.001) negative correlation of P100 amplitude and a statistically significant (P<0.05) positive correlation of N70 latency, P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Student's t-test. Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values. Conversely, as PSD increases the magnitude of VEP excursions were found to be diminished.

The effect of spectral filters on VEP and alpha-wave responses

PubMed Central

Willeford, Kevin T.; Fimreite, Vanessa; Ciuffreda, Kenneth J.

2015-01-01

Purpose Spectral filters are used to treat light sensitivity in individuals with traumatic brain injury (TBI); however, the effect of these filters on normal visual function has not been elucidated. Thus, the current study aimed to determine the effect of spectral filters on objectively-measured visual-evoked potential (VEP) and alpha-wave responses in the visually-normal population. Methods The full-field (15°H × 17°V), pattern-reversal VEP (20′ check size, mean luminance 52 cd/m2) was administered to 20 visually-normal individuals. They were tested with four Intuitive-Colorimeter-derived, broad-band, spectral filters (i.e., gray/neutral density, blue, yellow, and red), which produced similar luminance values for the test stimulus. The VEP N75 and P100 latencies, and VEP amplitude, were recorded. Power spectrum analysis was used to derive the respective powers at each frequency, and peak frequency, for the selected 9–11 Hz components of the alpha band. Results Both N75 and P100 latencies increased with the addition of each filter when compared to baseline. Additionally, each filter numerically reduced intra-session amplitude variability relative to baseline. There were no significant effects on either the mean VEP amplitude or alpha wave parameters. Conclusions The Intuitive Colorimeter filters significantly increased both N75 and P100 latencies, an effect which is primarily attributable (∼75%) to luminance, and in some cases, specific spectral effects (e.g., blue and red). VEP amplitude and alpha power were not significantly affected. These findings provide an important reference to which either amplitude or power changes in light-sensitive, younger clinical groups can be compared. PMID:26293969

Solution structure and dynamics of C-terminal regulatory domain of Vibrio vulnificus extracellular metalloprotease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yun, Ji-Hye; Kim, Heeyoun; Park, Jung Eun

Highlights: Black-Right-Pointing-Pointer We have determined solution structures of vEP C-terminal regulatory domain. Black-Right-Pointing-Pointer vEP C-ter100 has a compact {beta}-barrel structure with eight anti-parallel {beta}-strands. Black-Right-Pointing-Pointer Solution structure of vEP C-ter100 shares its molecular topology with that of the collagen-binding domain of collagenase. Black-Right-Pointing-Pointer Residues in the {beta}3 region of vEP C-ter100 might be important in putative ligand/receptor binding. Black-Right-Pointing-Pointer vEP C-ter100 interacts strongly with iron ion. -- Abstract: An extracellular metalloprotease (vEP) secreted by Vibrio vulnificus ATCC29307 is a 45-kDa proteolytic enzyme that has prothrombin activation and fibrinolytic activities during bacterial infection. The action of vEP could result in clottingmore » that could serve to protect the bacteria from the host defense machinery. Very recently, we showed that the C-terminal propeptide (C-ter100), which is unique to vEP, is involved in regulation of vEP activity. To understand the structural basis of this function of vEP C-ter100, we have determined the solution structure and backbone dynamics using multidimensional nuclear magnetic resonance spectroscopy. The solution structure shows that vEP C-ter100 is composed of eight anti-parallel {beta}-strands with a unique fold that has a compact {beta}-barrel formation which stabilized by hydrophobic and hydrogen bonding networks. Protein dynamics shows that the overall structure, including loops, is very rigid and stabilized. By structural database analysis, we found that vEP C-ter100 shares its topology with that of the collagen-binding domain of collagenase, despite low sequence homology between the two domains. Fluorescence assay reveals that vEP C-ter100 interacts strongly with iron (Fe{sup 3+}). These findings suggest that vEP protease might recruit substrate molecules, such as collagen, by binding at C-ter100 and that vEP participates in iron uptake from iron-withholding proteins of the host cell during infection.« less

Empirical mode decomposition processing to improve multifocal-visual-evoked-potential signal analysis in multiple sclerosis

PubMed Central

2018-01-01

Objective To study the performance of multifocal-visual-evoked-potential (mfVEP) signals filtered using empirical mode decomposition (EMD) in discriminating, based on amplitude, between control and multiple sclerosis (MS) patient groups, and to reduce variability in interocular latency in control subjects. Methods MfVEP signals were obtained from controls, clinically definitive MS and MS-risk progression patients (radiologically isolated syndrome (RIS) and clinically isolated syndrome (CIS)). The conventional method of processing mfVEPs consists of using a 1–35 Hz bandpass frequency filter (XDFT). The EMD algorithm was used to decompose the XDFT signals into several intrinsic mode functions (IMFs). This signal processing was assessed by computing the amplitudes and latencies of the XDFT and IMF signals (XEMD). The amplitudes from the full visual field and from ring 5 (9.8–15° eccentricity) were studied. The discrimination index was calculated between controls and patients. Interocular latency values were computed from the XDFT and XEMD signals in a control database to study variability. Results Using the amplitude of the mfVEP signals filtered with EMD (XEMD) obtains higher discrimination index values than the conventional method when control, MS-risk progression (RIS and CIS) and MS subjects are studied. The lowest variability in interocular latency computations from the control patient database was obtained by comparing the XEMD signals with the XDFT signals. Even better results (amplitude discrimination and latency variability) were obtained in ring 5 (9.8–15° eccentricity of the visual field). Conclusions Filtering mfVEP signals using the EMD algorithm will result in better identification of subjects at risk of developing MS and better accuracy in latency studies. This could be applied to assess visual cortex activity in MS diagnosis and evolution studies. PMID:29677200

Retinal nerve fibre thickness measured with optical coherence tomography accurately detects confirmed glaucomatous damage

PubMed Central

Hood, D C; Harizman, N; Kanadani, F N; Grippo, T M; Baharestani, S; Greenstein, V C; Liebmann, J M; Ritch, R

2007-01-01

Aim To assess the accuracy of optical coherence tomography (OCT) in detecting damage to a hemifield, patients with hemifield defects confirmed on both static automated perimetry (SAP) and multifocal visual evoked potentials (mfVEP) were studied. Methods Eyes of 40 patients with concomitant SAP and mfVEP glaucomatous loss and 25 controls underwent OCT retinal nerve fibre layer (RNFL), mfVEP and 24‐2 SAP tests. For the mfVEP and 24‐2 SAP, a hemifield was defined as abnormal based upon cluster criteria. On OCT, a hemifield was considered abnormal if one of the five clock hour sectors (3 and 9 o'clock excluded) was at <1% (red) or two were at <5% (yellow). Results Seventy seven (43%) of the hemifields were abnormal on both mfVEP and SAP tests. The OCT was abnormal for 73 (95%) of these. Only 1 (1%) of the 100 hemifields of the controls was abnormal on OCT. Sensitivity/specificity (one eye per person) was 95/98%. Conclusions The OCT RNFL test accurately detects abnormal hemifields confirmed on both subjective and objective functional tests. Identifying abnormal hemifields with a criterion of 1 red (1%) or 2 yellow (5%) clock hours may prove useful in clinical practice. PMID:17301118

A method to detect progression of glaucoma using the multifocal visual evoked potential technique

PubMed Central

Wangsupadilok, Boonchai; Kanadani, Fabio N.; Grippo, Tomas M.; Liebmann, Jeffrey M.; Ritch, Robert; Hood, Donald C.

2010-01-01

Purpose To describe a method for monitoring progression of glaucoma using the multifocal visual evoked potential (mfVEP) technique. Methods Eighty-seven patients diagnosed with open-angle glaucoma were divided into two groups. Group I, comprised 43 patients who had a repeat mfVEP test within 50 days (mean 0.9 ± 0.5 months), and group II, 44 patients who had a repeat test after at least 6 months (mean 20.7 ± 9.7 months). Monocular mfVEPs were obtained using a 60-sector pattern reversal dartboard display. Monocular and interocular analyses were performed. Data from the two visits were compared. The total number of abnormal test points with P < 5% within the visual field (total scores) and number of abnormal test points within a cluster (cluster size) were calculated. Data for group I provided a measure of test–retest variability independent of disease progression. Data for group II provided a possible measure of progression. Results The difference in the total scores for group II between visit 1 and visit 2 for the interocular and monocular comparison was significant (P < 0.05) as was the difference in cluster size for the interocular comparison (P < 0.05). Group I did not show a significant change in either total score or cluster size. Conclusion The change in the total score and cluster size over time provides a possible method for assessing progression of glaucoma with the mfVEP technique. PMID:18830654

Comparison of isolated-check visual evoked potential and standard automated perimetry in early glaucoma and high-risk ocular hypertension

PubMed Central

Chen, Xiang-Wu; Zhao, Ying-Xi

2017-01-01

AIM To compare the diagnostic performance of isolated-check visual evoked potential (icVEP) and standard automated perimetry (SAP), for evaluating the application values of icVEP in the detection of early glaucoma. METHODS Totally 144 subjects (288 eyes) were enrolled in this study. icVEP testing was performed with the Neucodia visual electrophysiological diagnostic system. A 15% positive-contrast (bright) condition pattern was used in this device to differentiate between glaucoma patients and healthy control subjects. Signal-to-noise ratios (SNR) were derived based on a multivariate statistic. The eyes were judged as abnormal if the test yielded an SNR≤1. SAP testing was performed with the Humphrey Field Analyzer II. The visual fields were deemed as abnormality if the glaucoma hemifield test results outside normal limits; or the pattern standard deviation with P<0.05; or the cluster of three or more non-edge points on the pattern deviation plot in a single hemifield with P<0.05, one of which must have a P<0.01. Disc photographs were graded as either glaucomatous optic neuropathy or normal by two experts who were masked to all other patient information. Moorfields regression analysis (MRA) used as a separate diagnostic classification was performed by Heidelberg retina tomograph (HRT). RESULTS When the disc photograph grader was used as diagnostic standard, the sensitivity for SAP and icVEP was 32.3% and 38.5% respectively and specificity was 82.3% and 77.8% respectively. When the MRA Classifier was used as the diagnostic standard, the sensitivity for SAP and icVEP was 48.6% and 51.4% respectively and specificity was 84.1% and 78.0% respectively. When the combined structural assessment was used as the diagnostic standard, the sensitivity for SAP and icVEP was 59.2% and 53.1% respectively and specificity was 84.2% and 84.6% respectivlely. There was no statistical significance between the sensitivity or specificity of SAP and icVEP, regardless of which diagnostic standard was based on. CONCLUSION The diagnostic performance of icVEP is not better than that of SAP in the detection of early glaucoma. PMID:28503434

Multifocal VEP and OCT findings in patients with primary open angle glaucoma: A cross-sectional study

PubMed Central

2012-01-01

Bakground To evaluate objectively the anatomical and functional changes of optic nerve in eyes with primary open angle glaucoma (POAG) by the joint use of optical coherence tomography (OCT) and multifocal visual evoked potentials (mfVEP). Methods 29 eyes with open angle glaucoma and visual field defects, as well as 20 eyes of 10 age-matched control normal subjects were tested. All participants underwent a complete ophthalmological examination. Moreover, Humphrey visual field test, OCT examination and recording of mfVEP were performed. Amplitude and implicit time of mfVEP, as well as RNFL thickness were measured. Differences in density components of mfVEP and in RNFL thickness among POAG eyes and control eyes were examined using Student’s t-test. Results In glaucomatous eyes the mean Retinal Response Density (RRD) was lower than normal in ring 1, 2 and 3 of mfVEP (p < 0.0001). Specifically the mean amplitude of mfVEP in POAG eyes was estimated at 34.2 ± 17.6 nV/deg2, 6.9 ± 4.8 nV/deg2 and 2.6 ± 1.6 nV/deg2 in rings 1, 2 and 3 respectively. In contrast the mean implicit time was similar to control eyes. In addition, the mean RNFL thickness in POAG eyes was estimated at 76.8 ± 26.6 μm in the superior area, 52.1 ± 16.3 μm in the temporal area, 75.9 ± 32.5 μm in the inferior area and 58.6 ± 19.4 μm in the nasal area. There was a statistically significant difference in RNFL thickness in all peripapillary areas (p < 0.0001) between POAG eyes and controls, with superior and inferior area to present the highest decrease. Conclusions Our study shows that, although Standard Automatic Perimetry is the gold standard to evaluate glaucomatous neuropathy, the joint use of mfVEP and OCT could be useful in better monitoring glaucoma progression. PMID:22856337

Transient VEP and psychophysical chromatic contrast thresholds in children and adults.

PubMed

Boon, Mei Ying; Suttle, Catherine M; Dain, Stephen J

2007-07-01

It has been found that humans are able to distinguish colours without luminance cues by about 2-4 months of age and that sensitivity to colour difference develops during childhood, reaching a peak around adolescence. This prolonged period of maturation is reflected by improvements in psychophysical threshold measures and by the VEP characteristics of morphology, latency and amplitude. An intra-individual comparison of VEP and psychophysical responses to isoluminant colour stimuli has not been made in children, however, and this was the aim of the present study. VEPs were recorded from 49 subjects, children (age range: 4.8-12.6 years) and adults (age range: 25.7-33.2 years). Psychophysical and VEP thresholds were both measured in 40 of those subjects. Nominally isoluminant chromatic (L-M) sinewave gratings were presented in onset-offset mode and identical stimuli were used for psychophysical and VEP recordings to allow comparison. In agreement with previous reports, morphology of the transient VEP in response to this stimulus differed considerably between children and adults. There was a significant difference between psychophysical and VEP thresholds in children, but not in adults. Our findings support and expand on previous work on maturation of the L-M chromatic pathway and indicate a larger discrepancy between VEP and psychophysical chromatic thresholds in children than in adults.

Multifocal blue-on-yellow visual evoked potentials in early glaucoma.

PubMed

Klistorner, Alexander; Graham, Stuart L; Martins, Alessandra; Grigg, John R; Arvind, Hemamalini; Kumar, Rajesh S; James, Andrew C; Billson, Francis A

2007-09-01

To determine the sensitivity and specificity of blue-on-yellow multifocal visual evoked potentials (mfVEPs) in early glaucoma. Cross-sectional study. Fifty patients with a confirmed diagnosis of early glaucoma and 60 normal participants. Black-and-white mfVEPs and blue-on-yellow mfVEPs were recorded using the Accumap version 2.0 (ObjectiVision Pty. Ltd., Sydney, Australia). All patients also underwent achromatic standard automated perimetry (SAP). Multifocal VEP amplitude and latency values in glaucoma patients were analyzed and compared with those of the normal controls. Based on the definition of visual field defect, in the group of glaucomatous eyes with SAP defects, amplitude of blue-on-yellow mfVEP was abnormal in all 64 cases (100% sensitivity), whereas black-and-white mfVEP missed 5 cases (92.2% sensitivity). Generally, larger scotomata were noted on blue-on-yellow mfVEP compared with black-and-white mfVEP for the same eyes. There was high topographic correspondence between SAP and amplitude of blue-on-yellow mfVEP and significant (P<0.0001) correlation between them (correlation coefficient, 0.73). Abnormal amplitude was detected in 3 of 60 eyes of control subjects (95% specificity). There was, however, no correlation between visual field defect and latency delay in glaucoma patients. Although there was a significant difference between averaged latency of control and glaucoma eyes, values considerably overlapped. The blue-on-yellow mfVEP is a sensitive and specific tool for detecting early glaucoma based on amplitude analysis.

Comparison of multifocal visual evoked potential, static automated perimetry, and optical coherence tomography findings for assessing visual pathways in patients with pituitary adenomas.

PubMed

Qiao, Nidan; Zhang, Yichao; Ye, Zhao; Shen, Ming; Shou, Xuefei; Wang, Yongfei; Li, Shiqi; Wang, Min; Zhao, Yao

2015-10-01

There have been no studies investigating the correlation between structural [thickness of the retinal nerve fiber layer (RNFL) as determined by optical coherence tomography (OCT)] and functional [Humphrey visual field (HVF) or visual evoked potential (VEP) amplitude] measures of optic nerve integrity in patients with pituitary adenomas (PA). Patients with PAs were recruited between September 2010 and September 2013. OCT, standard automated perimetry (SAP), and multifical VEP (mfVEP) were performed. Agreement between OCT, SAP, and mfVEP values in classifying eyes/quadrants was determined using AC1 statistics. Pearson's correlation was used to examine relationships between structural and functional data. In total, 88.7% of the eyes tested showed abnormal SAP findings and 93.7% showed abnormal mfVEP findings. Only 14.8% of the eyes showed abnormal OCT findings. The agreement between SAP and mfVEP findings was 88.9% (AC1 = 0.87). The agreement between OCT and mfVEP findings was 24.2% (AC1 = -0.52), and that between OCT and SAP findings was 21.5% (AC1 = -0.56). The correlation values between RNFL thickness and the functional measurements were -0.601 for the mfVEP score (P = 0.000) and -0.441 for the SAP score (P = 0.000). The correlation between the mfVEP and SAP scores was -0.617 (P = 0.000). mfVEP, SAP, and OCT provided complementary information for detecting visual pathway abnormalities in patients with PAs. Good agreement was demonstrated between SAP and mfVEP and quantitative analysis of structure-function measurements revealed a moderate correlation.

Dichoptic stimulation improves detection of glaucoma with multifocal visual evoked potentials.

PubMed

Arvind, Hemamalini; Klistorner, Alexander; Graham, Stuart; Grigg, John; Goldberg, Ivan; Klistorner, Asya; Billson, Frank A

2007-10-01

To determine whether simultaneous binocular (dichoptic) stimulation for multifocal visual evoked potentials (mfVEP) detects glaucomatous defects and decreases intereye variability. Twenty-eight patients with glaucoma and 30 healthy subjects underwent mfVEP on monocular and dichoptic stimulation. Dichoptic stimulation was presented with the use of virtual reality goggles (recording time, 7 minutes). Monocular mfVEPs were recorded sequentially for each eye (recording time, 10 minutes). Comparison of mean relative asymmetry coefficient (RAC; calculated as difference in amplitudes between eyes/sum of amplitudes of both eyes at each segment) on monocular and dichoptic mfVEP revealed significantly lower RAC on dichoptic (0.003 +/- 0.03) compared with monocular testing (-0.02 +/- 0.04; P = 0.002). In all 28 patients, dichoptic mfVEP identified defects with excellent topographic correspondence. Of 56 hemifields (28 eyes), 33 had Humphrey visual field (HFA) scotomas, all of which were detected by dichoptic mfVEP. Among 23 hemifields with normal HFA, two were abnormal on monocular and dichoptic mfVEP. Five hemifields (five patients) normal on HFA and monocular mfVEP were abnormal on dichoptic mfVEP. In all five patients, corresponding rim changes were observed on disc photographs. Mean RAC of glaucomatous eyes was significantly higher on dichoptic (0.283 +/- 0.18) compared with monocular (0.199 +/- 0.12) tests (P = 0.0006). Dichoptic mfVEP not only detects HFA losses, it may identify early defects in areas unaffected on HFA and monocular mfVEP while reducing testing time by 30%. Asymmetry was tighter among healthy subjects but wider in patients with glaucoma on simultaneous binocular stimulation, which is potentially a new tool in the early detection of glaucoma.

Effect of recording duration on the diagnostic performance of multifocal visual-evoked potentials in high-risk ocular hypertension and early glaucoma.

PubMed

Fortune, Brad; Zhang, Xian; Hood, Donald C; Demirel, Shaban; Patterson, Emily; Jamil, Annisa; Mansberger, Steven L; Cioffi, George A; Johnson, Chris A

2008-01-01

To evaluate the effect on diagnostic performance of reducing multifocal visual-evoked potential (mfVEP) recording duration from 16 to 8 minutes per eye. Both eyes of 185 individuals with high-risk ocular hypertension or early glaucoma were studied. Two 8-minute mfVEP recordings were obtained for each eye in an ABBA order using VERIS. The first recording for each eye was compared against single run (1-Run) mfVEP normative data; the average of both recordings for each eye was compared against 2-Run normative data. Visual fields (VFs) were obtained by standard automated perimetry (SAP) within 22.3+/-27.0 days of the mfVEP. Stereo disc photographs and Heidelberg Retina Tomograph images were obtained together, within 24.8+/-50.4 days of the mfVEP and 33.1+/-62.9 days of SAP. Masked experts graded disc photographs as either glaucomatous optic neuropathy or normal. The overall Moorfields Regression Analysis result from the Heidelberg Retina Tomograph was used as a separate diagnostic classification. Thus, 4 diagnostic standards were applied in total, 2 based on optic disc structure alone and 2 others based on disc structure and SAP. Agreement between the 1-Run and 2-Run mfVEP was 90%. Diagnostic performance of the 1-Run mfVEP was similar to that of the 2-Run mfVEP for all 4 diagnostic standards. Sensitivity was slightly higher for the 2-Run mfVEP, whereas specificity was slightly higher for the 1-Run mfVEP. If higher sensitivity is sought, the 2-Run mfVEP will provide better discrimination between groups of eyes with relatively high signal-to-noise ratio (eg, early glaucoma or high-risk suspects). But if higher specificity is a more important goal, the 1-Run mfVEP provides adequate sensitivity and requires only half the test time. Considered alongside prior studies, the present results suggest that the 1-Run mfVEP is an efficient way to confirm (or refute) the extent of VF loss in patients with moderate or advanced glaucoma, particularly in those with unreliable VFs, including malingering or other "functional" forms of VF loss.

Combining MRI and VEP imaging to isolate the temporal response of visual cortical areas

NASA Astrophysics Data System (ADS)

Carney, Thom; Ales, Justin; Klein, Stanley A.

2008-02-01

The human brain has well over 30 cortical areas devoted to visual processing. Classical neuro-anatomical as well as fMRI studies have demonstrated that early visual areas have a retinotopic organization whereby adjacent locations in visual space are represented in adjacent areas of cortex within a visual area. At the 2006 Electronic Imaging meeting we presented a method using sprite graphics to obtain high resolution retinotopic visual evoked potential responses using multi-focal m-sequence technology (mfVEP). We have used this method to record mfVEPs from up to 192 non overlapping checkerboard stimulus patches scaled such that each patch activates about 12 mm2 of cortex in area V1 and even less in V2. This dense coverage enables us to incorporate cortical folding constraints, given by anatomical MRI and fMRI results from the same subject, to isolate the V1 and V2 temporal responses. Moreover, the method offers a simple means of validating the accuracy of the extracted V1 and V2 time functions by comparing the results between left and right hemispheres that have unique folding patterns and are processed independently. Previous VEP studies have been contradictory as to which area responds first to visual stimuli. This new method accurately separates the signals from the two areas and demonstrates that both respond with essentially the same latency. A new method is introduced which describes better ways to isolate cortical areas using an empirically determined forward model. The method includes a novel steady state mfVEP and complex SVD techniques. In addition, this evolving technology is put to use examining how stimulus attributes differentially impact the response in different cortical areas, in particular how fast nonlinear contrast processing occurs. This question is examined using both state triggered kernel estimation (STKE) and m-sequence "conditioned kernels". The analysis indicates different contrast gain control processes in areas V1 and V2. Finally we show that our m-sequence multi-focal stimuli have advantages for integrating EEG and MEG for improved dipole localization.

The correlation dimension: a useful objective measure of the transient visual evoked potential?

PubMed

Boon, Mei Ying; Henry, Bruce I; Suttle, Catherine M; Dain, Stephen J

2008-01-14

Visual evoked potentials (VEPs) may be analyzed by examination of the morphology of their components, such as negative (N) and positive (P) peaks. However, methods that rely on component identification may be unreliable when dealing with responses of complex and variable morphology; therefore, objective methods are also useful. One potentially useful measure of the VEP is the correlation dimension. Its relevance to the visual system was investigated by examining its behavior when applied to the transient VEP in response to a range of chromatic contrasts (42%, two times psychophysical threshold, at psychophysical threshold) and to the visually unevoked response (zero contrast). Tests of nonlinearity (e.g., surrogate testing) were conducted. The correlation dimension was found to be negatively correlated with a stimulus property (chromatic contrast) and a known linear measure (the Fourier-derived VEP amplitude). It was also found to be related to visibility and perception of the stimulus such that the dimension reached a maximum for most of the participants at psychophysical threshold. The latter suggests that the correlation dimension may be useful as a diagnostic parameter to estimate psychophysical threshold and may find application in the objective screening and monitoring of congenital and acquired color vision deficiencies, with or without associated disease processes.

Evaluation of Hemifield Sector Analysis Protocol in Multifocal Visual Evoked Potential Objective Perimetry for the Diagnosis and Early Detection of Glaucomatous Field Defects

PubMed Central

Mousa, Mohammad F.; Cubbidge, Robert P.; Al-Mansouri, Fatima

2014-01-01

Purpose Multifocal visual evoked potential (mfVEP) is a newly introduced method used for objective visual field assessment. Several analysis protocols have been tested to identify early visual field losses in glaucoma patients using the mfVEP technique, some were successful in detection of field defects, which were comparable to the standard automated perimetry (SAP) visual field assessment, and others were not very informative and needed more adjustment and research work. In this study we implemented a novel analysis approach and evaluated its validity and whether it could be used effectively for early detection of visual field defects in glaucoma. Methods Three groups were tested in this study; normal controls (38 eyes), glaucoma patients (36 eyes) and glaucoma suspect patients (38 eyes). All subjects had a two standard Humphrey field analyzer (HFA) test 24-2 and a single mfVEP test undertaken in one session. Analysis of the mfVEP results was done using the new analysis protocol; the hemifield sector analysis (HSA) protocol. Analysis of the HFA was done using the standard grading system. Results Analysis of mfVEP results showed that there was a statistically significant difference between the three groups in the mean signal to noise ratio (ANOVA test, p < 0.001 with a 95% confidence interval). The difference between superior and inferior hemispheres in all subjects were statistically significant in the glaucoma patient group in all 11 sectors (t-test, p < 0.001), partially significant in 5 / 11 (t-test, p < 0.01), and no statistical difference in most sectors of the normal group (1 / 11 sectors was significant, t-test, p < 0.9). Sensitivity and specificity of the HSA protocol in detecting glaucoma was 97% and 86%, respectively, and for glaucoma suspect patients the values were 89% and 79%, respectively. Conclusions The new HSA protocol used in the mfVEP testing can be applied to detect glaucomatous visual field defects in both glaucoma and glaucoma suspect patients. Using this protocol can provide information about focal visual field differences across the horizontal midline, which can be utilized to differentiate between glaucoma and normal subjects. Sensitivity and specificity of the mfVEP test showed very promising results and correlated with other anatomical changes in glaucoma field loss. PMID:24511212

The role of visual evoked potential and electroretinography in the preoperative assessment of osteo-keratoprosthesis or osteo-odonto-keratoprosthesis surgery.

PubMed

de Araujo, Aline L; Charoenrook, Victor; de la Paz, Maria F; Temprano, Jose; Barraquer, Rafael I; Michael, Ralph

2012-09-01

To determine the value of electroretinography (ERG) and visual evoked potential (VEP) in predicting visual outcome in patients undergoing osteo-keratoprosthesis (OKP) or osteo-odonto-keratoprosthesis (OOKP) surgery. We performed a retrospective cohort study of 143 eyes in 101 patients who underwent OKP or OOKP surgery. The subjects underwent ERG, VEP testing or both up to 6 months prior to surgery. The ERG and VEP results were classified into four categories based on wave amplitude, latency and configuration. The main outcome was the maximum best-corrected visual acuity (maxBCVA) reached at any time postoperatively. One hundred thirty-four cases had undergone preoperative ERG, 82 VEP and 73 both examinations. The sensitivities of ERG and VEP to detect maxBCVA≥0.05 were 68.5% and 87%, respectively, while the specificity was 63.2% for ERG and 47.4% for VEP. The maxBCVA was significantly better in patients with normal ERG (p=0.033) and those with normal VEP (p=0.048), once having defined appropriate normal and abnormal cut-off levels. When comparing fellow eyes in patients who underwent surgery in both eyes, maxBCVA was better in the eyes that had better VEP results (p=0.013). Eyes demonstrating normal ERG or VEP achieved better visual outcome than those with abnormal results. In addition, VEP proved instrumental in determining the eye with the best prognosis when comparing both eyes of a given patient. © 2011 The Authors. Acta Ophthalmologica © 2011 Acta Ophthalmologica Scandinavica Foundation.

Effect of binasal occlusion (BNO) and base-in prisms on the visual-evoked potential (VEP) in mild traumatic brain injury (mTBI).

PubMed

Yadav, Naveen K; Ciuffreda, Kenneth J

2014-01-01

To assess quantitatively the effect and relative contribution of binasal occlusion (BNO) and base-in prisms (BI) on visually-evoked potential (VEP) responsivity in persons with mild traumatic brain injury (mTBI) and the symptom of visual motion sensitivity (VMS), as well as in visually-normal (VN) individuals. Subjects were comprised of 20 VN adults and 15 adults with mTBI and VMS. There were four test conditions: (1) conventional pattern VEP, which served as the baseline comparison condition; (2) VEP with BNO alone; (3) VEP with 2 pd BI prisms before each eye; and (4) VEP with the above BNO and BI prism combination. In mTBI, the mean VEP amplitude increased significantly in nearly all subjects (∼90%) with BNO alone. In contrast, in VN, it decreased significantly with BNO alone in all subjects (100%), as compared to the other test conditions. These objective findings were consistent with improvements in visual impressions and sensorimotor tasks in the group with mTBI. Latency remained within normal limits under all test conditions in both groups. Only the BNO condition demonstrated significant, but opposite and consistent, directional effects on the VEP amplitude in both groups. The BNO-VEP test condition may be used clinically for the objectively-based, differential diagnosis of persons suspected of having mTBI and VMS from the VNs.

Implantation and Recording of Wireless Electroretinogram and Visual Evoked Potential in Conscious Rats.

PubMed

Charng, Jason; He, Zheng; Bui, Bang; Vingrys, Algis; Ivarsson, Magnus; Fish, Rebecca; Gurrell, Rachel; Nguyen, Christine

2016-06-29

The full-field electroretinogram (ERG) and visual evoked potential (VEP) are useful tools to assess retinal and visual pathway integrity in both laboratory and clinical settings. Currently, preclinical ERG and VEP measurements are performed with anesthesia to ensure stable electrode placements. However, the very presence of anesthesia has been shown to contaminate normal physiological responses. To overcome these anesthesia confounds, we develop a novel platform to assay ERG and VEP in conscious rats. Electrodes are surgically implanted sub-conjunctivally on the eye to assay the ERG and epidurally over the visual cortex to measure the VEP. A range of amplitude and sensitivity/timing parameters are assayed for both the ERG and VEP at increasing luminous energies. The ERG and VEP signals are shown to be stable and repeatable for at least 4 weeks post surgical implantation. This ability to record ERG and VEP signals without anesthesia confounds in the preclinical setting should provide superior translation to clinical data.

Detailed spatiotemporal brain mapping of chromatic vision combining high-resolution VEP with fMRI and retinotopy.

PubMed

Pitzalis, Sabrina; Strappini, Francesca; Bultrini, Alessandro; Di Russo, Francesco

2018-03-13

Neuroimaging studies have identified so far, several color-sensitive visual areas in the human brain, and the temporal dynamics of these activities have been separately investigated using the visual-evoked potentials (VEPs). In the present study, we combined electrophysiological and neuroimaging methods to determine a detailed spatiotemporal profile of chromatic VEP and to localize its neural generators. The accuracy of the present co-registration study was obtained by combining standard fMRI data with retinotopic and motion mapping data at the individual level. We found a sequence of occipito activities more complex than that typically reported for chromatic VEPs, including feed-forward and reentrant feedback. Results showed that chromatic human perception arises by the combined activity of at the least five parieto-occipital areas including V1, LOC, V8/VO, and the motion-sensitive dorsal region MT+. However, the contribution of V1 and V8/VO seems dominant because the re-entrant activity in these areas was present more than once (twice in V8/VO and thrice in V1). This feedforward and feedback chromatic processing appears delayed compared with the luminance processing. Associating VEPs and neuroimaging measures, we showed for the first time a complex spatiotemporal pattern of activity, confirming that chromatic stimuli produce intricate interactions of many different brain dorsal and ventral areas. © 2018 Wiley Periodicals, Inc.

Objective perimetry using a four-channel multifocal VEP system: correlation with conventional perimetry and thickness of the retinal nerve fibre layer.

PubMed

Horn, Folkert K; Kaltwasser, Christoph; Jünemann, Anselm G; Kremers, Jan; Tornow, Ralf P

2012-04-01

There is evidence that multifocal visual evoked potentials (VEPs) can be used as an objective tool to detect visual field loss. The aim of this study was to correlate multifocal VEP amplitudes with standard perimetry data and retinal nerve fibre layer (RNFL) thickness. Multifocal VEP recordings were performed with a four-channel electrode array using 58 stimulus fields (pattern reversal dartboard). For each field, the recording from the channel with maximal signal-to-noise ratio (SNR) was retained, resulting in an SNR optimised virtual recording. Correlation with RNFL thickness, measured with spectral domain optical coherence tomography and with standard perimetry, was performed for nerve fibre bundle related areas. The mean amplitudes in nerve fibre related areas were smaller in glaucoma patients than in normal subjects. The differences between both groups were most significant in mid-peripheral areas. Amplitudes in these areas were significantly correlated with corresponding RNFL thickness (Spearman R=0.76) and with standard perimetry (R=0.71). The multifocal VEP amplitude was correlated with perimetric visual field data and the RNFL thickness of the corresponding regions. This method of SNR optimisation is useful for extracting data from recordings and may be appropriate for objective assessment of visual function at different locations. This study has been registered at http://www.clinicaltrials.gov (NCT00494923).

Reference layer adaptive filtering (RLAF) for EEG artifact reduction in simultaneous EEG-fMRI.

PubMed

Steyrl, David; Krausz, Gunther; Koschutnig, Karl; Edlinger, Günter; Müller-Putz, Gernot R

2017-04-01

Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) combines advantages of both methods, namely high temporal resolution of EEG and high spatial resolution of fMRI. However, EEG quality is limited due to severe artifacts caused by fMRI scanners. To improve EEG data quality substantially, we introduce methods that use a reusable reference layer EEG cap prototype in combination with adaptive filtering. The first method, reference layer adaptive filtering (RLAF), uses adaptive filtering with reference layer artifact data to optimize artifact subtraction from EEG. In the second method, multi band reference layer adaptive filtering (MBRLAF), adaptive filtering is performed on bandwidth limited sub-bands of the EEG and the reference channels. The results suggests that RLAF outperforms the baseline method, average artifact subtraction, in all settings and also its direct predecessor, reference layer artifact subtraction (RLAS), in lower (<35 Hz) frequency ranges. MBRLAF is computationally more demanding than RLAF, but highly effective in all EEG frequency ranges. Effectivity is determined by visual inspection, as well as root-mean-square voltage reduction and power reduction of EEG provided that physiological EEG components such as occipital EEG alpha power and visual evoked potentials (VEP) are preserved. We demonstrate that both, RLAF and MBRLAF, improve VEP quality. For that, we calculate the mean-squared-distance of single trial VEP to the mean VEP and estimate single trial VEP classification accuracies. We found that the average mean-squared-distance is lowest and the average classification accuracy is highest after MBLAF. RLAF was second best. In conclusion, the results suggests that RLAF and MBRLAF are potentially very effective in improving EEG quality of simultaneous EEG-fMRI. Highlights We present a new and reusable reference layer cap prototype for simultaneous EEG-fMRI We introduce new algorithms for reducing EEG artifacts due to simultaneous fMRI The algorithms combine a reference layer and adaptive filtering Several evaluation criteria suggest superior effectivity in terms of artifact reduction We demonstrate that physiological EEG components are preserved.

Reference layer adaptive filtering (RLAF) for EEG artifact reduction in simultaneous EEG-fMRI

NASA Astrophysics Data System (ADS)

Steyrl, David; Krausz, Gunther; Koschutnig, Karl; Edlinger, Günter; Müller-Putz, Gernot R.

2017-04-01

Objective. Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) combines advantages of both methods, namely high temporal resolution of EEG and high spatial resolution of fMRI. However, EEG quality is limited due to severe artifacts caused by fMRI scanners. Approach. To improve EEG data quality substantially, we introduce methods that use a reusable reference layer EEG cap prototype in combination with adaptive filtering. The first method, reference layer adaptive filtering (RLAF), uses adaptive filtering with reference layer artifact data to optimize artifact subtraction from EEG. In the second method, multi band reference layer adaptive filtering (MBRLAF), adaptive filtering is performed on bandwidth limited sub-bands of the EEG and the reference channels. Main results. The results suggests that RLAF outperforms the baseline method, average artifact subtraction, in all settings and also its direct predecessor, reference layer artifact subtraction (RLAS), in lower (<35 Hz) frequency ranges. MBRLAF is computationally more demanding than RLAF, but highly effective in all EEG frequency ranges. Effectivity is determined by visual inspection, as well as root-mean-square voltage reduction and power reduction of EEG provided that physiological EEG components such as occipital EEG alpha power and visual evoked potentials (VEP) are preserved. We demonstrate that both, RLAF and MBRLAF, improve VEP quality. For that, we calculate the mean-squared-distance of single trial VEP to the mean VEP and estimate single trial VEP classification accuracies. We found that the average mean-squared-distance is lowest and the average classification accuracy is highest after MBLAF. RLAF was second best. Significance. In conclusion, the results suggests that RLAF and MBRLAF are potentially very effective in improving EEG quality of simultaneous EEG-fMRI. Highlights We present a new and reusable reference layer cap prototype for simultaneous EEG-fMRI We introduce new algorithms for reducing EEG artifacts due to simultaneous fMRI The algorithms combine a reference layer and adaptive filtering Several evaluation criteria suggest superior effectivity in terms of artifact reduction We demonstrate that physiological EEG components are preserved

Repeatability of normal multifocal VEP: implications for detecting progression.

PubMed

Fortune, Brad; Demirel, Shaban; Zhang, Xian; Hood, Donald C; Johnson, Chris A

2006-04-01

To assess the repeatability of the multifocal visual evoked potential (mfVEP) and to compare it with the repeatability of standard automated perimetry (SAP) in the same group of 50 normal controls retested after 1 year. Our second aim was to assess the repeatability of false alarm rates determined previously for the mfVEP using various cluster criteria. Fifty individuals with normal vision participated in this study (33 females and 17 males). The age range was 26.7 to 77.9 years and the group average age (+/- SD) was 51.4 (+/- 12.1) years. Pattern-reversal mfVEPs were obtained using a dartboard stimulus pattern in VERIS and two 8-minute runs per eye were averaged. The average number of days between the first and second mfVEP tests was 378 (+/- 58). SAP visual fields were obtained within 17.4 (+/- 20.3) days of the mfVEP using the SITA-standard threshold algorithm. Repeatability of mfVEPs and SAP total deviation values were evaluated by calculating point-wise limits of agreement (LOA). Specificity (1-false alarm rate) was evaluated for a range of cluster criteria, whereby the number and probability level of the points defining a cluster were varied. Point-wise LOA for the mfVEP signal-to-noise ratio (SNR) ranged from 2.0 to 4.3 dB, with an average of 2.9 dB across all 60 locations. For SAP, LOA ranged from 2.4 to 8.9 dB, with an average of 4.0 dB (excluding the points immediately above and below the blind spot). Clusters of abnormal points were not likely to repeat on either mfVEP or SAP. When an mfVEP abnormality was defined as the repeat presence (confirmation) of a 3-point (P < 0.05) cluster anywhere within a single hemifield, only 1 (of 200) monocular hemifield was deemed abnormal. Although the LOA of the mfVEP were similar throughout the field, the limited dynamic range of SNR at superior field locations will limit the ability to follow progression in "depth" at those locations. Repeatability of the mfVEP was slightly better than SAP visual fields in this group of controls with a 1-year retest interval. This suggests that progression in early stages should be more easily detectable by mfVEP. However, in certain field locations (eg, superior periphery), the relatively more narrow dynamic range of the SNR of the mfVEP may limit detection of progression to just 1 event. Confirmation of a 3-point cluster abnormality is highly suggestive of a true defect on the mfVEP.

Spatial decoupling of targets and flashing stimuli for visual brain-computer interfaces

NASA Astrophysics Data System (ADS)

Waytowich, Nicholas R.; Krusienski, Dean J.

2015-06-01

Objective. Recently, paradigms using code-modulated visual evoked potentials (c-VEPs) have proven to achieve among the highest information transfer rates for noninvasive brain-computer interfaces (BCIs). One issue with current c-VEP paradigms, and visual-evoked paradigms in general, is that they require direct foveal fixation of the flashing stimuli. These interfaces are often visually unpleasant and can be irritating and fatiguing to the user, thus adversely impacting practical performance. In this study, a novel c-VEP BCI paradigm is presented that attempts to perform spatial decoupling of the targets and flashing stimuli using two distinct concepts: spatial separation and boundary positioning. Approach. For the paradigm, the flashing stimuli form a ring that encompasses the intended non-flashing targets, which are spatially separated from the stimuli. The user fixates on the desired target, which is classified using the changes to the EEG induced by the flashing stimuli located in the non-foveal visual field. Additionally, a subset of targets is also positioned at or near the stimulus boundaries, which decouples targets from direct association with a single stimulus. This allows a greater number of target locations for a fixed number of flashing stimuli. Main results. Results from 11 subjects showed practical classification accuracies for the non-foveal condition, with comparable performance to the direct-foveal condition for longer observation lengths. Online results from 5 subjects confirmed the offline results with an average accuracy across subjects of 95.6% for a 4-target condition. The offline analysis also indicated that targets positioned at or near the boundaries of two stimuli could be classified with the same accuracy as traditional superimposed (non-boundary) targets. Significance. The implications of this research are that c-VEPs can be detected and accurately classified to achieve comparable BCI performance without requiring potentially irritating direct foveation of flashing stimuli. Furthermore, this study shows that it is possible to increase the number of targets beyond the number of stimuli without degrading performance. Given the superior information transfer rate of c-VEP paradigms, these results can lead to the development of more practical and ergonomic BCIs.

Pattern Electroretinography and Visual Evoked Potentials Provide Clinical Evidence of CNS Modulation of High- and Low-Contrast VEP Latency in Glaucoma

PubMed Central

Sponsel, William E.; Johnson, Susan L.; Trevino, Rick; Gonzalez, Alberto; Groth, Sylvia L.; Majcher, Carolyn; Fulton, Diane C.; Reilly, Matthew A.

2017-01-01

Purpose Both pattern electroretinography (PERG) and visual evoked potentials (VEP) can be performed using low- (15%; Lc) and high- (85%; Hc) contrast gratings that may preferentially stimulate the magno- and parvocellular pathways. We observed that among glaucomatous patients showing only one VEP latency deficit per eye, there appeared to be a very strong tendency for an Hc delay in one eye and an Lc delay in the other. Methods Diopsys NOVA-LX system was used to measure VEP Hc and Lc latency among a clinical glaucoma population to find all individuals with either a single Hc or Lc latency abnormality in each eye (group 1), or with greater than 0 and less than 4 Hc or Lc VEP latency abnormalities in the two eyes (group 2) to determine whether a significant inverse correlation existed for these values in either group. Hc and Lc PERG data were also evaluated to assess associated retinal ganglion cell responses. Results A strong inverse correlation (P = 0.0000003) was observed between the Hc and Lc VEP latency values among the 64 eyes in group 1. Group 2 provided a comparable result (n = 143; 286 eyes; P = 0.0005). PERG (n = 81; 162 eyes) also showed strong bilateral symmetry for magnitude values (P < 0.0001 for both Lc and Hc in groups 1 and 2). Conclusions Bilateral retention of both low-resolution/high-speed and high-resolution/low-speed function may persist with both eyes open despite symmetrically pathologic retinal ganglion cell PERG waveform asynchrony for Hc and Lc stimuli in the paired eyes. Translational Relevance Clinical electrophysiology strongly suggests binocular compensation for dynamic dysfunction operates under central nervous system (CNS) control in glaucoma. PMID:29134137

Steady-state multifocal visual evoked potential (ssmfVEP) using dartboard stimulation as a possible tool for objective visual field assessment.

PubMed

Horn, Folkert K; Selle, Franziska; Hohberger, Bettina; Kremers, Jan

2016-02-01

To investigate whether a conventional, monitor-based multifocal visual evoked potential (mfVEP) system can be used to record steady-state mfVEP (ssmfVEP) in healthy subjects and to study the effects of temporal frequency, electrode configuration and alpha waves. Multifocal pattern reversal VEP measurements were performed at 58 dartboard fields using VEP recording equipment. The responses were measured using m-sequences with four pattern reversals per m-step. Temporal frequencies were varied between 6 and 15 Hz. Recordings were obtained from nine normal subjects with a cross-shaped, four-electrode device (two additional channels were derived). Spectral analyses were performed on the responses at all locations. The signal to noise ratio (SNR) was computed for each response using the signal amplitude at the reversal frequency and the noise at the neighbouring frequencies. Most responses in the ssmfVEP were significantly above noise. The SNR was largest for an 8.6-Hz reversal frequency. The individual alpha electroencephalogram (EEG) did not strongly influence the results. The percentage of the records in which each of the 6 channels had the largest SNR was between 10.0 and 25.2 %. Our results in normal subjects indicate that reliable mfVEP responses can be achieved by steady-state stimulation using a conventional dartboard stimulator and multi-channel electrode device. The ssmfVEP may be useful for objective visual field assessment as spectrum analysis can be used for automated evaluation of responses. The optimal reversal frequency is 8.6 Hz. Alpha waves have only a minor influence on the analysis. Future studies must include comparisons with conventional mfVEP and psychophysical visual field tests.

Longitudinal assessment of childhood optic gliomas: relationship between flicker visual evoked potentials and magnetic resonance imaging findings.

PubMed

Falsini, Benedetto; Ziccardi, Lucia; Lazzareschi, Ilaria; Ruggiero, Antonio; Placentino, Luca; Dickmann, Anna; Liotti, Lucia; Piccardi, Marco; Balestrazzi, Emilio; Colosimo, Cesare; Di Rocco, Concezio; Riccardi, Riccardo

2008-05-01

The aim of this study was to evaluate longitudinally functional and neuro-radiologic findings in childhood optic gliomas (OG), by comparing flicker visual evoked potentials (F-VEPs) with brain magnetic resonance imaging (MRI) changes. Fourteen children (age range: 1-13 years) with OGs underwent serial F-VEP, MRI and neuro-ophthalmic examinations over a 38 month (median, range: 6-76) follow-up. F-VEPs were elicited by 8 Hz sine-wave flicker stimuli presented in a mini-Ganzfeld. Contrast-enhanced MRI examinations were performed. Results of both tests were blindly assessed by independent evaluators. F-VEPs were judged to be improved, stable or worsened if changes in the amplitude and/or phase angle of the response exceeded the limits of test-retest variability (+/-90th percentile) established for the same patients. MRI results were judged to show regression, stabilization or progression of OG based on its changes in size (+/-20%) or extension. Two to seven pairs of F-VEP/MRI examinations per patient (median: 4) were collected. Based on a total of 38 pairs of F-VEP/MRI examinations, both tests agreed in showing worsening (progression), stabilization and improvement (regression) in 5, 15 and 10 cases, respectively. In 3 cases, F-VEPs showed a worsening and MRI a stabilization, while in 5 cases F-VEPs showed an improvement and MRI a stabilization. Agreement between F-VEP and MRI changes was 78.9% (95% CI: +/- 37%, K statistics = 0.67, P < 0.001). The results indicate that longitudinal F-VEP changes can predict changes in MRI-assessed OG size and extension, providing a non-invasive functional assay, complementary to neuro-imaging, for OG follow-up.

Clinical use of multifocal visual-evoked potentials in a glaucoma practice: a prospective study.

PubMed

De Moraes, Carlos Gustavo; Liebmann, Jeffrey M; Ritch, Robert; Hood, Donald C

2012-08-01

To test a framework that describes how the multifocal visual-evoked potential (mfVEP) technique is used in a particular glaucoma practice. In this prospective, descriptive study, glaucoma suspects, ocular hypertensives and glaucoma patients were referred for mfVEP testing by a single glaucoma specialist over a 2-year period. All patients underwent standard automated perimetry (SAP) and mfVEP testing within 3 months. Two hundred and ten patients (420 eyes) were referred for mfVEP testing for the following reasons: (1) normal SAP tests suspected of early functional loss (ocular hypertensives, n = 43; and glaucoma suspects on the basis of suspicious optic disks, n = 52); (2) normal-tension glaucoma patients with suspected central SAP defects (n = 33); and (3) SAP abnormalities needing confirmation (n = 82). All the glaucoma suspects with normal SAP and mfVEP results remained untreated. Of those with abnormal mfVEP results, 68 % (15/22) were treated because the abnormal regions on the mfVEP were consistent with the abnormal regions seen during clinical examination of the optic disk. The mfVEP was abnormal in 86 % (69/80) of eyes with glaucomatous optic neuropathy and SAP damage, even though it did not result in an altered treatment regimen. In NTG patients, the mfVEP showed central defects in 44 % (12 of 27) of the eyes with apparently normal central fields and confirmed central scotomata in 92 % (36 of 39), leading to more rigorous surveillance of these patients. In a clinical practice, the mfVEP was used when clinical examination and subjective visual fields provided insufficient or conflicting information. This information influenced clinical management.

Functional assessment of the visual pathway with multifocal visual evoked potentials, and their relationship with disability in patients with multiple sclerosis.

PubMed

Blanco, Román; Pérez-Rico, Consuelo; Puertas-Muñoz, Inmaculada; Ayuso-Peralta, Lucía; Boquete, Luciano; Arévalo-Serrano, Juan

2014-02-01

To objectively evaluate the visual function, and the relationship between disability and optic nerve dysfunction, in patients with multiple sclerosis (MS) and optic neuritis (ON), using multifocal visual evoked potentials (mfVEP). This observational, cross-sectional study assessed 28 consecutive patients with clinically definite MS, according to the McDonald criteria, and 19 age-matched healthy subjects. Disability was recorded using the Expanded Disability Status Scale (EDSS) score. The patients' mfVEP were compared to their clinical, psychophysical (Humphrey perimetry) and structural (optic coherence tomography (OCT)) diagnostic test data. We observed a significant agreement between mfVEP amplitude and Humphrey perimetry/OCT in MS-ON eyes, and between mfVEP amplitude and OCT in MS but non-ON eyes. We found significant differences in EDSS score between patients with abnormal and normal mfVEP amplitudes. Abnormal mfVEP amplitude defects (from interocular and monocular probability analysis) were found in 67.9% and 73.7% of the MS-ON and MS-non-ON group eyes, respectively. Delayed mfVEP latencies (interocular and monocular probability analysis) were seen in 70.3% and 73.7% of the MS-ON and MS-non-ON groups, respectively. We found a significant relationship between mfVEP amplitude and disease severity, as measured by EDSS score, that suggested there is a role for mfVEP amplitude as a functional biomarker of axonal loss in MS.

3D graphics, virtual reality, and motion-onset visual evoked potentials in neurogaming.

PubMed

Beveridge, R; Wilson, S; Coyle, D

2016-01-01

A brain-computer interface (BCI) offers movement-free control of a computer application and is achieved by reading and translating the cortical activity of the brain into semantic control signals. Motion-onset visual evoked potentials (mVEP) are neural potentials employed in BCIs and occur when motion-related stimuli are attended visually. mVEP dynamics are correlated with the position and timing of the moving stimuli. To investigate the feasibility of utilizing the mVEP paradigm with video games of various graphical complexities including those of commercial quality, we conducted three studies over four separate sessions comparing the performance of classifying five mVEP responses with variations in graphical complexity and style, in-game distractions, and display parameters surrounding mVEP stimuli. To investigate the feasibility of utilizing contemporary presentation modalities in neurogaming, one of the studies compared mVEP classification performance when stimuli were presented using the oculus rift virtual reality headset. Results from 31 independent subjects were analyzed offline. The results show classification performances ranging up to 90% with variations in conditions in graphical complexity having limited effect on mVEP performance; thus, demonstrating the feasibility of using the mVEP paradigm within BCI-based neurogaming. © 2016 Elsevier B.V. All rights reserved.

Using a cVEP-Based Brain-Computer Interface to Control a Virtual Agent.

PubMed

Riechmann, Hannes; Finke, Andrea; Ritter, Helge

2016-06-01

Brain-computer interfaces provide a means for controlling a device by brain activity alone. One major drawback of noninvasive BCIs is their low information transfer rate, obstructing a wider deployment outside the lab. BCIs based on codebook visually evoked potentials (cVEP) outperform all other state-of-the-art systems in that regard. Previous work investigated cVEPs for spelling applications. We present the first cVEP-based BCI for use in real-world settings to accomplish everyday tasks such as navigation or action selection. To this end, we developed and evaluated a cVEP-based on-line BCI that controls a virtual agent in a simulated, but realistic, 3-D kitchen scenario. We show that cVEPs can be reliably triggered with stimuli in less restricted presentation schemes, such as on dynamic, changing backgrounds. We introduce a novel, dynamic repetition algorithm that allows for optimizing the balance between accuracy and speed individually for each user. Using these novel mechanisms in a 12-command cVEP-BCI in the 3-D simulation results in ITRs of 50 bits/min on average and 68 bits/min maximum. Thus, this work supports the notion of cVEP-BCIs as a particular fast and robust approach suitable for real-world use.

Multifocal visual evoked potential and automated perimetry abnormalities in strabismic amblyopes.

PubMed

Greenstein, Vivienne C; Eggers, Howard M; Hood, Donald C

2008-02-01

To compare visual field abnormalities obtained with standard automated perimetry (SAP) to those obtained with the multifocal visual evoked potential (mfVEP) technique in strabismic amblyopes. Humphrey 24-2 visual fields (HVF) and mfVEPs were obtained from each eye of 12 strabismic amblyopes. For the mfVEP, amplitudes and latencies were analyzed and probability plots were derived. Multifocal VEP and HVF hemifields were abnormal if they had clusters of two or more contiguous points at p < 0.01, or three or more contiguous points at p < 0.05 with at least one at p < 0.01. An eye was abnormal if it had an abnormal hemifield. On SAP, amblyopic eyes had significantly higher foveal thresholds (p = 0.003) and lower mean deviation values (p = 0.005) than fellow eyes. For the mfVEP, 11 amblyopic and 6 fellow eyes were abnormal. Of the 11 amblyopic eyes, 6 were abnormal on SAP. The deficits extended from the center to mid periphery. Monocular mfVEP latencies were significantly decreased for amblyopic eyes compared with control eyes (p < 0.0002). Both techniques revealed deficits in visual function across the visual field in strabismic amblyopes, but the mfVEP revealed deficits in fellow eyes and in more amblyopic eyes. In addition, mfVEP response latencies for amblyopic eyes were shorter than normal.

Effect of head circumference on parameters of pattern reversal visual evoked potential in healthy adults of central India.

PubMed

Kothari, R; Singh, R; Singh, S; Bokariya, P

2012-06-01

Visual evoked response testing has been one of the most exciting clinical tools to be developed from neurophysiologic research in recent years and has provided us with an objective method of identifying abnormalities of the afferent visual pathways. Investigation were carried out to see whether the head circumference influence the pattern reversal visual evoked potential (PRVEP) parameters. The study comprised of pattern reversal visual evoked potential (PRVEP) recordings in 400 eyes of 200 normal subjects. Two hundred fourty eight eyes were males and 152 eyes were from 76 female subjects recruited from the Central Indian population in the age range of 40-79 years. Visual evoked potential (VEP) recordings were performed in accordance to the standardized methodology of International Federation of Clinical Neurophysiology (IFCN) Committee Recommendations and International Society for Clinical Electrophysiology of Vision (ISCEV) Guidelines and montages were kept as per 10-20 International System of EEG Electrode placements. The stimulus configuration in this study consisted of the transient pattern reversal method in which a black and white checker board was generated (full field) and displayed on a VEP Monitor by an electronic pattern regenerator inbuilt in an Evoked Potential Recorder (RMS EMG EP MARK II). VEP latencies, duration and amplitude were measured in all subjects and the data were analyzed. The correlation of all the electrophysiological parameters with head circumference was evaluated by Pearson's correlation co-efficient (r) and its statistical significance was evaluated. The prediction equations for all the VEP parameters with respect to head circumference were derived. We found a positive correlation of P 100 latency and N 155 latency with mean head circumference, while a highly significant negative correlation were noted of P 100 amplitude with head circumference. N 70 latency was significantly correlated with head circumference. P 100 duration showed in negative correlation with head circumference. These findings suggest that VEP latencies, duration and amplitude are influenced by the head circumference of the individual in a sample of healthy subjects and head circumference can be a useful predictor of VEP peak latencies, amplitude and duration.

Occlusion therapy improves phase-alignment of the cortical response in amblyopia.

PubMed

Kelly, John P; Tarczy-Hornoch, Kristina; Herlihy, Erin; Weiss, Avery H

2015-09-01

The visual evoked potential (VEP) generated by the amblyopic visual system demonstrates reduced amplitude, prolonged latency, and increased variation in response timing (phase-misalignment). This study examined VEPs before and after occlusion therapy (OT) and whether phase-misalignment can account for the amblyopic VEP deficits. VEPs were recorded to 0.5-4cycles/degree gratings in 10 amblyopic children (2-6years age) before and after OT. Phase-misalignment was measured by Fourier analysis across a limited bandwidth. Signal-to-noise ratios (SNRs) were estimated from amplitude and phase synchrony in the Fourier domain. Responses were compared to VEPs corrected for phase-misalignment (individual epochs shifted in time to correct for the misalignment). Before OT, amblyopic eyes (AE) had significantly more phase-misalignment, latency prolongation, and lower SNR relative to the fellow eye. Phase-misalignment contributed significantly to low SNR but less so to latency delay in the AE. After OT, phase-alignment improved, SNR improved and latency shortened in the AE. Raw averaged waveforms from the AE improved after OT, primarily at higher spatial frequencies. Correcting for phase-misalignment in the AE sharpened VEP peak responses primarily at low spatial frequencies, but could not account for VEP waveform improvements in the AE after OT at higher spatial frequencies. In summary, VEP abnormalities from the AE are associated with phase-misalignment and reduced SNR possibly related to desynchronization of neuronal activity. The effect of OT on VEP responses is greater than that accounted for by phase-misalignment and SNR alone. Copyright © 2014 Elsevier Ltd. All rights reserved.

[Relationship between magnocellular function and reading skills in children: a study using visual evoked potentials].

PubMed

Kobayashi, Tomoka; Inagaki, Masumi; Yamazaki, Hiroko; Kita, Yosuke; Kaga, Makiko; Oka, Akira

2014-11-01

Developmental dyslexia (DD) is a neurodevelopmental disorder that is characterized by difficulties with accurate and/or fluent word recognition and by poor spelling and decoding abilities. The magnocellular deficit theory is one of several hypotheses that have been proposed to explain the pathophysiology of DD. In this study, we investigated magnocellular system dysfunction in Japanese dyslexic children. Subjects were 19 dyslexic children (DD group) and 19 aged-matched healthy children (TD group). They were aged between 7 and 16 years. Reversed patterns of black and white sinusoidal gratings generated at a low spatial frequency, high reversal frequency of 7.5 Hz, and low contrasts were used specifically to stimulate the magnocellular system. We recorded visual evoked potentials (VEP) from the occipital area and examined their relationship with reading and naming tasks, such as the time to read hiragana characters, rapid automatized naming of pictured objects, and phonological manipulation. Compared to the TD group, the DD group showed a significantly lower peak amplitude of VEPs through the complex demodulation method. Structural equation modeling showed that VEP peak amplitudes were related to the rapid automatized naming of pictured objects, and better rapid automatized naming resulted in higher reading skills. There was no correlation between VEP findings and the capacity for phonological manipulation. VEPs in response to the magnocellular system are useful for understanding the pathophysiology of DD. Single phonological deficit may not be sufficient to cause DD.

Visuocortical Function in Infants With a History of Neonatal Jaundice

PubMed Central

Hou, Chuan; Norcia, Anthony M.; Madan, Ashima; Good, William V.

2014-01-01

Purpose. High concentrations of unconjugated bilirubin are neurotoxic and cause brain damage in newborn infants. However, the exact level of bilirubin that may be neurotoxic in a given infant is unknown. The aim of this study was to use a quantitative measure of neural activity, the swept parameter visual evoked potential (sVEP) to determine the relationship between neonatal bilirubin levels and visual responsivity several months later. Methods. We compared sVEP response functions over a wide range of contrast, spatial frequency, and Vernier offset sizes in 16 full-term infants with high bilirubin levels (>10 mg/dL) and 18 age-matched infants with no visible neonatal jaundice, all enrolled at 14 to 22 weeks of age. The group means of sVEP thresholds and suprathreshold response amplitudes were compared. The correlation between individual sVEP thresholds and bilirubin levels in jaundiced infants was studied. Results. Infants who had a history of neonatal jaundice showed lower response amplitudes (P < 0.05) and worse or immeasurable sVEP thresholds compared with control infants for all three measures (P < 0.05). Swept parameter visual evoked potential thresholds for Vernier offset were correlated with bilirubin level (P < 0.05), but spatial acuity and contrast sensitivity measures in the infants with neonatal jaundice were not (P > 0.05). Conclusions. These results indicate that elevated neonatal bilirubin levels affect measures of visual function in infancy up to at least 14 to 22 weeks of postnatal age. PMID:25183760

The extraction of motion-onset VEP BCI features based on deep learning and compressed sensing.

PubMed

Ma, Teng; Li, Hui; Yang, Hao; Lv, Xulin; Li, Peiyang; Liu, Tiejun; Yao, Dezhong; Xu, Peng

2017-01-01

Motion-onset visual evoked potentials (mVEP) can provide a softer stimulus with reduced fatigue, and it has potential applications for brain computer interface(BCI)systems. However, the mVEP waveform is seriously masked in the strong background EEG activities, and an effective approach is needed to extract the corresponding mVEP features to perform task recognition for BCI control. In the current study, we combine deep learning with compressed sensing to mine discriminative mVEP information to improve the mVEP BCI performance. The deep learning and compressed sensing approach can generate the multi-modality features which can effectively improve the BCI performance with approximately 3.5% accuracy incensement over all 11 subjects and is more effective for those subjects with relatively poor performance when using the conventional features. Compared with the conventional amplitude-based mVEP feature extraction approach, the deep learning and compressed sensing approach has a higher classification accuracy and is more effective for subjects with relatively poor performance. According to the results, the deep learning and compressed sensing approach is more effective for extracting the mVEP feature to construct the corresponding BCI system, and the proposed feature extraction framework is easy to extend to other types of BCIs, such as motor imagery (MI), steady-state visual evoked potential (SSVEP)and P300. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of binasal occlusion (BNO) on the visual-evoked potential (VEP) in mild traumatic brain injury (mTBI).

PubMed

Ciuffreda, Kenneth J; Yadav, Naveen K; Ludlam, Diana P

2013-01-01

The purpose of the experiment was to assess the effect of binasal occlusion (BNO) on the visually-evoked potential (VEP) in visually-normal (VN) individuals and in those with mild traumatic brain injury (mTBI) for whom BNO frequently reduces their primary symptoms related to abnormally-increased visual motion sensitivity (VMS). Subjects were comprised of asymptomatic VN adults (n = 10) and individuals with mTBI (n = 10) having the symptom of VMS. Conventional full-field VEP testing was employed under two conditions: without BNO and with opaque BNO which blocked regions on either side of the VEP test stimulus. Subjective impressions were also assessed. In VN, the mean VEP amplitude decreased significantly with BNO in all subjects. In contrast, in mTBI, the mean VEP amplitude increased significantly with BNO in all subjects. Latency was normal and unaffected in all cases. Repeat VEP testing in three subjects from each group revealed similar test-re-test findings. Visuomotor activities improved, with reduced symptoms, with BNO in the mTBI group. It is speculated that individuals with mTBI habitually attempt to suppress visual information in the near retinal periphery to reduce their abnormal VMS, with addition of the BNO negating the suppressive influence and thus producing a widespread disinhibition effect and resultant increase in VEP amplitude.

Diagnosis of Normal and Abnormal Color Vision with Cone-Specific VEPs.

PubMed

Rabin, Jeff C; Kryder, Andrew C; Lam, Dan

2016-05-01

Normal color vision depends on normal long wavelength (L), middle wavelength (M), and short wavelength sensitive (S) cones. Hereditary "red-green" color vision deficiency (CVD) is due to a shift in peak sensitivity or lack of L or M cones. Hereditary S cone CVD is rare but can be acquired as an early sign of disease. Current tests detect CVD but few diagnose type or severity, critical for linking performance to real-world demands. The anomaloscope and newer subjective tests quantify CVD but are not applicable to infants or cognitively impaired patients. Our purpose was to develop an objective test of CVD with sensitivity and specificity comparable to current tests. A calibrated visual-evoked potential (VEP) display and Food and Drug Administration-approved system was used to record L, M, and S cone-specific pattern-onset VEPs from 18 color vision normals (CVNs) and 13 hereditary CVDs. VEP amplitudes and latencies were compared between groups to establish VEP sensitivity and specificity. Cone VEPs show 100% sensitivity for diagnosis of CVD and 94% specificity for confirming CVN. L cone (protan) CVDs showed a significant increase in L cone latency (53.1 msec, P < 0.003) and decreased amplitude (10.8 uV, P < 0.0000005) but normal M and S cone VEPs ( P > 0.31). M cone (deutan) CVDs showed a significant increase in M cone latency (31.0 msec, P < 0.000004) and decreased amplitude (8.4 uV, P < 0.006) but normal L and S cone VEPs ( P > 0.29). Cone-specific VEPs offer a rapid, objective test to diagnose hereditary CVD and show potential for detecting acquired CVD in various diseases. This paper describes the efficacy of cone-specific color VEPs for quantification of normal and abnormal color vision. The rapid, objective nature of this approach makes it suitable for detecting color sensitivity loss in infants and the cognitively impaired.

Nonlinear dynamics of cortical responses to color in the human cVEP.

PubMed

Nunez, Valerie; Shapley, Robert M; Gordon, James

2017-09-01

The main finding of this paper is that the human visual cortex responds in a very nonlinear manner to the color contrast of pure color patterns. We examined human cortical responses to color checkerboard patterns at many color contrasts, measuring the chromatic visual evoked potential (cVEP) with a dense electrode array. Cortical topography of the cVEPs showed that they were localized near the posterior electrode at position Oz, indicating that the primary cortex (V1) was the major source of responses. The choice of fine spatial patterns as stimuli caused the cVEP response to be driven by double-opponent neurons in V1. The cVEP waveform revealed nonlinear color signal processing in the V1 cortex. The cVEP time-to-peak decreased and the waveform's shape was markedly narrower with increasing cone contrast. Comparison of the linear dynamics of retinal and lateral geniculate nucleus responses with the nonlinear dynamics of the cortical cVEP indicated that the nonlinear dynamics originated in the V1 cortex. The nature of the nonlinearity is a kind of automatic gain control that adjusts cortical dynamics to be faster when color contrast is greater.

A process evaluation of implementing a vocational enablement protocol for employees with hearing difficulties in clinical practice.

PubMed

Gussenhoven, Arjenne H M; Singh, Amika S; Goverts, S Theo; van Til, Marten; Anema, Johannes R; Kramer, Sophia E

2015-08-01

A multidisciplinary vocational rehabilitation programme, the Vocational Enablement Protocol (VEP) was developed to address the specific needs of employees with hearing difficulties. In the current study we evaluated the process of implementing the VEP in audiologic care among employees with hearing impairment. In conjunction with a randomized controlled trial, we collected and analysed data on seven process parameters: recruitment, reach, fidelity, dose delivered, dose received and implemented, satisfaction, and perceived benefit. Sixty-six employees with hearing impairment participated in the VEP. The multidisciplinary team providing the VEP comprised six professionals. The professionals performed the VEP according to the protocol. Of the recommendations delivered by the professionals, 31% were perceived as implemented by the employees. Compliance rate was highest for hearing-aid uptake (51%). Both employees and professionals were highly satisfied with the VEP. Participants rated good perceived benefit from it. Our results indicate that the VEP could be a useful treatment for employees with hearing difficulties from a process evaluation perspective. Implementation research in the audiological setting should be encouraged in order to further provide insight into parameters facilitating or hindering successful implementation of an intervention and to improve its quality and efficacy.

Comparison of visual evoked potential monitoring during spine surgeries under total intravenous anesthesia versus balanced general anesthesia.

PubMed

Uribe, Alberto A; Mendel, Ehud; Peters, Zoe A; Shneker, Bassel F; Abdel-Rasoul, Mahmoud; Bergese, Sergio D

2017-10-01

To determine the comparison of its clinical utility and safety profile for visual evoked potential (VEP) monitoring during prone spine surgeries under total intravenous anesthesia (TIVA) versus balanced general anesthesia using the SightSaver™ visual stimulator. The protocol was designed asa pilot, single center, prospective, randomized, and double-arm study. Subjects were randomized to receive either TIVA or balanced general anesthesia. Following induction and intubation, 8 electrodes were placed subcutaneously to collect VEP recordings. The SightSaver™ visual stimulator was placed on the subject's scalp before prone positioning. VEP waveforms were recorded every 30min and assessed by a neurophysiologist throughout the length of surgery. A total of 19 subjects were evaluated and VEP waveforms were successfully collected. TIVA group showed higher amplitude and lower latency than balanced anesthesia. Our data suggested that TIVA is associated with higher VEP amplitude and shorter latencies than balanced general anesthesia; therefore, TIVA could be the most efficient anesthesia regimen for VEP monitoring. The findings help to better understand the effect of different anesthesia regimens on intra-operative VEP monitoring. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Detecting early functional damage in glaucoma suspect and ocular hypertensive patients with the multifocal VEP technique.

PubMed

Thienprasiddhi, Phamornsak; Greenstein, Vivienne C; Chu, David H; Xu, Li; Liebmann, Jeffrey M; Ritch, Robert; Hood, Donald C

2006-08-01

To determine whether the multifocal visual evoked potential (mfVEP) technique can detect early functional damage in ocular hypertensive (OHT) and glaucoma suspect (GS) patients with normal standard achromatic automated perimetry (SAP) results. Twenty-five GS patients (25 eyes), 25 patients with OHT (25 eyes), and 50 normal controls (50 eyes) were enrolled in this study. All GS, OHT and normal control eyes had normal SAP as defined by a pattern standard deviation and mean deviation within the 95% confidence interval and a glaucoma hemifield test within normal limits on the Humphrey visual field 24-2 program. Eyes with GS had optic disc changes consistent with glaucoma with or without raised intraocular pressure (IOP), and eyes with OHT showed no evidence of glaucomatous optic neuropathy and IOPs >or=22 mm Hg. Monocular mfVEPs were obtained from both eyes of each subject using a pattern-reversal dartboard array with 60 sectors. The entire display had a radius of 22.3 degrees. The mfVEPs, for each eye, were defined as abnormal when either the monocular or interocular probability plot had a cluster of 3 or more contiguous points with P<0.05 and at least 2 of these points with P<0.01. The mfVEP results were abnormal in 4% of the eyes from normal subjects. Abnormal mfVEPs were detected in 20% of the eyes of GS patients and 16% of the eyes of OHT patients. Significantly more mfVEP abnormalities were detected in GS patients than in normal controls. However, there was no significant difference in mfVEP results between OHT patients and normal controls. The mfVEP technique can detect visual field deficits in a minority of eyes with glaucomatous optic disks and normal SAP results.

Simultaneous recording of multifocal VEP responses to short-wavelength and achromatic stimuli

PubMed Central

Wang, Min; Hood, Donald C.

2010-01-01

A paradigm is introduced that allows for simultaneous recording of the pattern-onset multifocal visual evoked potentials (mfVEP) to both short-wavelength (SW) and achromatic (A) stimuli. There were 5 sets of stimulus conditions, each of which is defined by two semi-concurrently presented stimuli, A64/SW (a 64% contrast achromatic stimulus and a short-wavelength stimulus), A64/A8 (64% achromatic/8% achromatic), A0/A8 (0% (gray) achromatic/8% achromatic), A64/A0 and A0/SW. When paired with A64 as part of A64/SW, the SW stimulus yielded mfVEP responses (SWmfVEP) with diminished amplitude in the fovea, consistent with the known sensitivity of the S-cone system. In addition, when A8, which is approximately equal to the L and M cone contribution of the SW stimulus, was recorded alone, the response to A8 was small, but significantly larger than noise. However, when A8 was paired with A64, the response to A8 was reduced to close to noise level, suggesting that the LM cone contribution of the SWmfVEP can be suppressed by A64. When A64 was recorded alone, the response to A64 was about 32% larger than the mfVEP for A64 when paired with the SW. Likewise, the presence of A64 stimulus also reduces the response of SWmfVEP by 35%. Finally, an intense narrow-band yellow background prolonged the latency of SW response for the A0/SW stimulus but not the latency of SW response for the A64/SW stimulus. These results indicate that it is possible to simultaneously record an SWmfVEP with little LM cone contribution along with an achromatic mfVEP. PMID:20499134

Normalization of auditory evoked potential and visual evoked potential in patients with idiot savant.

PubMed

Chen, X; Zhang, M; Wang, J; Lou, F; Liang, J

1999-03-01

To investigate the variations of auditory evoked potentials (AEP) and visual evoked potentials (VEP) of patients with idiot savant (IS) syndrome. Both AEP and VEP were recorded from 7 patients with IS syndrome, 21 mentally retarded (MR) children without the syndrome and 21 normally age-matched controls, using a Dantec concerto SEEG-16 BEAM instrument. Both AEP and VEP of MR group showed significantly longer latencies (P1 and P2 latencies of AEP, P < 0.01; N1 and N2 latencies of VEP, P < 0.01/0.05), lower P2 amplitudes (P < 0.01) and higher P3 amplitudes (P < 0.01), as compared with normal controls. But none of above-mentioned changes was found with IS group. Almost all MR patients (90.1%) presented P4 component in both AEP and VEP, which was also in sharp contrast with its incidence in other 2 groups (IS: 14.3%; normal controls: 9.5%). Patients with idiot savant syndrome presented normalized AEP and VEP.

Changes in visual-evoked potential habituation induced by hyperventilation in migraine.

PubMed

Coppola, Gianluca; Currà, Antonio; Sava, Simona Liliana; Alibardi, Alessia; Parisi, Vincenzo; Pierelli, Francesco; Schoenen, Jean

2010-12-01

Hyperventilation is often associated with stress, an established trigger factor for migraine. Between attacks, migraine is associated with a deficit in habituation to visual-evoked potentials (VEP) that worsens just before the attack. Hyperventilation slows electroencephalographic (EEG) activity and decreases the functional response in the occipital cortex during visual stimulation. The neural mechanisms underlying deficient-evoked potential habituation in migraineurs remain unclear. To find out whether hyperventilation alters VEP habituation, we recorded VEPs before and after experimentally induced hyperventilation lasting 3 min in 18 healthy subjects and 18 migraine patients between attacks. We measured VEP P100 amplitudes in six sequential blocks of 100 sweeps and habituation as the change in amplitude over the six blocks. In healthy subjects, hyperventilation decreased VEP amplitude in block 1 and abolished the normal VEP habituation. In migraine patients, hyperventilation further decreased the already low block 1 amplitude and worsened the interictal habituation deficit. Hyperventilation worsens the habituation deficit in migraineurs possibly by increasing dysrhythmia in the brainstem-thalamo-cortical network.

Can Local Voluntary Environmental Programs "Work"? An Examination of Fort Collins' (Colorado) Climate Wise Program

NASA Astrophysics Data System (ADS)

Samantha, Mosier; Jonathan, Fisk

2013-05-01

Previous research on voluntary environmental programs (VEPs) frequently assesses the effectiveness of federal, state, and third party programs and why organizations seek to join such programs. Yet, research has yet to evaluate the effectiveness or firm motivation relative to local VEPs. Recognizing this gap, our paper examines the structure and organization of Fort Collins' Climate Wise program, a local VEP. Using a variety of sources, we find that the program has successfully met both short- and long-term goals by persistently self-evaluating and seeking outside financial support. Findings from this analysis can aid in understanding and developing local VEPs elsewhere. Specifically, this initial research suggests that local VEPs need to consider local context and available resources when implementing such programs. Furthermore, it is possible for local VEPs to attract a diverse variety of participating firms by avoiding one-size-fits-all participation levels and by establishing a sense of ownership among partners.

Can local voluntary environmental programs "work"? An examination of Fort Collins' (Colorado) climate wise program.

PubMed

Mosier, Samantha; Samantha, Mosier; Fisk, Jonathan; Jonathan, Fisk

2013-05-01

Previous research on voluntary environmental programs (VEPs) frequently assesses the effectiveness of federal, state, and third party programs and why organizations seek to join such programs. Yet, research has yet to evaluate the effectiveness or firm motivation relative to local VEPs. Recognizing this gap, our paper examines the structure and organization of Fort Collins' Climate Wise program, a local VEP. Using a variety of sources, we find that the program has successfully met both short- and long-term goals by persistently self-evaluating and seeking outside financial support. Findings from this analysis can aid in understanding and developing local VEPs elsewhere. Specifically, this initial research suggests that local VEPs need to consider local context and available resources when implementing such programs. Furthermore, it is possible for local VEPs to attract a diverse variety of participating firms by avoiding one-size-fits-all participation levels and by establishing a sense of ownership among partners.

Voluntary Environmental Programs: A Comparative Perspective

ERIC Educational Resources Information Center

Prakash, Aseem; Potoski, Matthew

2012-01-01

Voluntary environmental programs (VEPs) are institutions for inducing firms to produce environmental goods beyond legal requirements. A comparative perspective on VEPs shows how incentives to sponsor and participate in VEPs vary across countries in ways that reveal their potential and limitations. Our brief survey examines conditions under which…

Comparison of pattern VEP results acquired using CRT and TFT stimulators in the clinical practice.

PubMed

Nagy, Balázs Vince; Gémesi, Szabolcs; Heller, Dávid; Magyar, András; Farkas, Agnes; Abrahám, György; Varsányi, Balázs

2011-06-01

There are several electrophysiological systems available commercially. Usually, control groups are required to compare their results, due to the differences between display types. Our aim was to examine the differences between CRT and LCD/TFT stimulators used in pattern VEP responses performed according to the ISCEV standards. We also aimed to check different contrast values toward thresholds. In order to obtain more precise results, we intended to measure the intensity and temporal response characteristics of the monitors with photometric methods. To record VEP signals, a Roland RetiPort electrophysiological system was used. The pattern VEP tests were carried out according to ISCEV protocols on a CRT and a TFT monitor consecutively. Achromatic checkerboard pattern was used at three different contrast levels (maximal, 75, 25%) using 1° and 15' check sizes. Both CRT and TFT displays were luminance and contrast matched, according to the gamma functions based on measurements at several DAC values. Monitor-specific luminance parameters were measured by means of spectroradiometric instruments. Temporal differences between the displays' electronic and radiometric signals were measured with a device specifically built for the purpose. We tested six healthy control subjects with visual acuity of at least 20/20. The tests were performed on each subject three times on different days. We found significant temporal differences between the CRT and the LCD monitors at all contrast levels and spatial frequencies. In average, the latency times were 9.0 ms (±3.3 ms) longer with the TFT stimulator. This value is in accordance with the average of the measured TFT input-output temporal difference values (10.1 ± 2.2 ms). According to our findings, measuring the temporal parameters of the TFT monitor with an adequately calibrated measurement setup and correcting the VEP data with the resulting values, the VEP signals obtained with different display types can be transformed to be comparable.

Visual processing during recovery from vegetative state to consciousness: comparing behavioral indices to brain responses.

PubMed

Wijnen, V J M; Eilander, H J; de Gelder, B; van Boxtel, G J M

2014-11-01

Auditory stimulation is often used to evoke responses in unresponsive patients who have suffered severe brain injury. In order to investigate visual responses, we examined visual evoked potentials (VEPs) and behavioral responses to visual stimuli in vegetative patients during recovery to consciousness. Behavioral responses to visual stimuli (visual localization, comprehension of written commands, and object manipulation) and flash VEPs were repeatedly examined in eleven vegetative patients every two weeks for an average period of 2.6months, and patients' VEPs were compared to a healthy control group. Long-term outcome of the patients was assessed 2-3years later. Visual response scores increased during recovery to consciousness for all scales: visual localization, comprehension of written commands, and object manipulation. VEP amplitudes were smaller, and latencies were longer in the patient group relative to the controls. VEPs characteristics at first measurement were related to long-term outcome up to three years after injury. Our findings show the improvement of visual responding with recovery from the vegetative state to consciousness. Elementary visual processing is present, yet according to VEP responses, poorer in vegetative and minimally conscious state than in healthy controls, and remains poorer when patients recovered to consciousness. However, initial VEPs are related to long-term outcome. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

[Visual evoked potentials in management of amblyopia in children].

PubMed

Gromová, M; Gerinec, A

2010-11-01

The authors want to point out the possibility of using the visual evoked potentials (VEP) in the diagnostic process of amblyopia, especially in preverbal children. We also researched the possibility of screening for amblyopia with VEP in young patients with anisometropia without strabismus being present, especially those who come from affected families. The authors followed changes in the course of an occlusion therapy and suggest that VEP could be used to predict a success of the amblyopia therapy. We analyzed group of 45 pediatric patients ages 2-10 years who were investigated in years 2006-2009 at Pediatric Ophthalmology Department of Children University Hospital in Bratislava with amblyopia. This group was compared with a control group of 25 healthy children. The cause of amblyopia in a majority of children (29 patients) was hyperopic anisometropia, 13 children had hyperopic isometropia, 3 patients had myopia over -3D. These causes in 22 children were combined with strabismus. The monocular pattern of VEP was evaluated in all patients. In cooperative children (25) we also evaluated binocular pattern of VEP. 18 patients with amblyopia had a second VEP evaluation done during the occlusion therapy, among those were 23 amblyopic eyes. The time frame from the first VEP evaluation to the second VEP evaluation was 1-11 months, average 5,1 months. The material was statistically evaluated. Our study showed statistically significant prolongation of the latency of both P and N2 waves (p = 0.01) in children with amblyopia.This can be used in diagnostic process of amblyopia in preverbal children as well as in the screening for amblyopia. We also followed changes during the occlusion therapy and we discovered persistent prolongation of the latency of the P wave and also changes in the amplitudes (p = 0.05) During repeated measurements and with applied therapy one can follow the dynamics of amblyopia, course of therapy by VEP changes. Results of our research suggest a great contribution of VEP especially in the diagnosis of anisometropic amblyopia, especially in preverbal children. The advantage of VEP is in the screening, prediction and dynamics of therapy too. The amblyopia management is a long lasting process requiring a thorough communication and cooperation among the patient, parent and a doctor.

Combination of blood oxygen level–dependent functional magnetic resonance imaging and visual evoked potential recordings for abnormal visual cortex in two types of amblyopia

PubMed Central

Wang, Xinmei; Cui, Dongmei; Zheng, Ling; Yang, Xiao; Yang, Hui

2012-01-01

Purpose To elucidate the different neuromechanisms of subjects with strabismic and anisometropic amblyopia compared with normal vision subjects using blood oxygen level–dependent functional magnetic resonance imaging (BOLD-fMRI) and pattern-reversal visual evoked potential (PR-VEP). Methods Fifty-three subjects, age range seven to 12 years, diagnosed with strabismic amblyopia (17 cases), anisometropic amblyopia (20 cases), and normal vision (16 cases), were examined using the BOLD-fMRI and PR-VEP of UTAS-E3000 techniques. Cortical activation by binocular viewing of reversal checkerboard patterns was examined in terms of the calcarine region of interest (ROI)-based and spatial frequency–dependent analysis. The correlation of cortical activation in fMRI and the P100 amplitude in VEP were analyzed using the SPSS 12.0 software package. Results In the BOLD-fMRI procedure, reduced areas and decreased activation levels were found in Brodmann area (BA) 17 and other extrastriate areas in subjects with amblyopia compared with the normal vision group. In general, the reduced areas mainly resided in the striate visual cortex in subjects with anisometropic amblyopia. In subjects with strabismic amblyopia, a more significant cortical impairment was found in bilateral BA 18 and BA 19 than that in subjects with anisometropic amblyopia. The activation by high-spatial-frequency stimuli was reduced in bilateral BA 18 and 19 as well as BA 17 in subjects with anisometropic amblyopia, whereas the activation was mainly reduced in BA 18 and BA 19 in subjects with strabismic amblyopia. These findings were further confirmed by the ROI-based analysis of BA 17. During spatial frequency–dependent VEP detection, subjects with anisometropic amblyopia had reduced sensitivity for high spatial frequency compared to subjects with strabismic amblyopia. The cortical activation in fMRI with the calcarine ROI-based analysis of BA 17 was significantly correlated with the P100 amplitude in VEP recording. Conclusions This study suggested that different types of amblyopia had different cortical responses and combinations of spatial frequency–dependent BOLD-fMRI with PR-VEP could differentiate among various kinds of amblyopia according to the different cortical responses. This study can supply new methods for amblyopia neurology study. PMID:22539870

Objective assessment of chromatic and achromatic pattern adaptation reveals the temporal response properties of different visual pathways.

PubMed

Robson, Anthony G; Kulikowski, Janus J

2012-11-01

The aim was to investigate the temporal response properties of magnocellular, parvocellular, and koniocellular visual pathways using increment/decrement changes in contrast to elicit visual evoked potentials (VEPs). Static achromatic and isoluminant chromatic gratings were generated on a monitor. Chromatic gratings were modulated along red/green (R/G) or subject-specific tritanopic confusion axes, established using a minimum distinct border criterion. Isoluminance was determined using minimum flicker photometry. Achromatic and chromatic VEPs were recorded to contrast increments and decrements of 0.1 or 0.2 superimposed on the static gratings (masking contrast 0-0.6). Achromatic increment/decrement changes in contrast evoked a percept of apparent motion when the spatial frequency was low; VEPs to such stimuli were positive in polarity and largely unaffected by high levels of static contrast, consistent with transient response mechanisms. VEPs to finer achromatic gratings showed marked attenuation as static contrast was increased. Chromatic VEPs to R/G or tritan chromatic contrast increments were of negative polarity and showed progressive attenuation as static contrast was increased, in keeping with increasing desensitization of the sustained responses of the color-opponent visual pathways. Chromatic contrast decrement VEPs were of positive polarity and less sensitive to pattern adaptation. The relative contribution of sustained/transient mechanisms to achromatic processing is spatial frequency dependent. Chromatic contrast increment VEPs reflect the sustained temporal response properties of parvocellular and koniocellular pathways. Cortical VEPs can provide an objective measure of pattern adaptation and can be used to probe the temporal response characteristics of different visual pathways.

Evaluation of multifocal visual evoked potentials in patients with Graves' orbitopathy and subclinical optic nerve involvement.

PubMed

Pérez-Rico, Consuelo; Rodríguez-González, Natividad; Arévalo-Serrano, Juan; Blanco, Román

2012-08-01

Dysthyroid optic neuropathy is the most serious, although infrequent (8-10 %) complication in Graves' orbitopathy (GO). It is known that early stages of compressive optic neuropathy may produce reversible visual field defects, suggesting axoplasmic stasis rather than ganglion cell death. This observational, cross-sectional, case-control study assessed 34 consecutive patients (65 eyes) with Graves' hyperthyroidism and longstanding GO and 31 age-matched control subjects. The patients' multifocal visual evoked potentials (mfVEP) were compared to their clinical and psychophysical (standard automated perimetry [SAP]) and structural (optic coherence tomography [OCT]) diagnostic test data. Abnormal cluster defects were found in 12.3 % and 3.1 % of eyes on the interocular and monocular amplitude analysis mfVEP probability plots, respectively. As well, mfVEP latencies delays were found in 13.8 and 20 % of eyes on the interocular and monocular analysis probability plots, respectively. Interestingly, 19 % of patients with GO had ocular hypertension, and a strong correlation between intraocular pressure measured at upgaze and mfVEP latency was found. MfVEP amplitudes and visual acuity were significantly related to each other (P < 0.05), but not with the latencies delays. However, relationships between the interocular or monocular mfVEP amplitudes and latencies analysis and SAP indices or OCT data were not statistically significant. One-third of our patients with GO showed changes in the mfVEP, indicating significant subclinical optic nerve dysfunction. In this sense, the mfVEP may be a useful diagnostic tool in the clinic for early diagnosis and monitoring of optic nerve function abnormalities in patients with GO.

Aging effect in pattern, motion and cognitive visual evoked potentials.

PubMed

Kuba, Miroslav; Kremláček, Jan; Langrová, Jana; Kubová, Zuzana; Szanyi, Jana; Vít, František

2012-06-01

An electrophysiological study on the effect of aging on the visual pathway and various levels of visual information processing (primary cortex, associate visual motion processing cortex and cognitive cortical areas) was performed. We examined visual evoked potentials (VEPs) to pattern-reversal, motion-onset (translation and radial motion) and visual stimuli with a cognitive task (cognitive VEPs - P300 wave) at luminance of 17 cd/m(2). The most significant age-related change in a group of 150 healthy volunteers (15-85 years of age) was the increase in the P300 wave latency (2 ms per 1 year of age). Delays of the motion-onset VEPs (0.47 ms/year in translation and 0.46 ms/year in radial motion) and the pattern-reversal VEPs (0.26 ms/year) and the reductions of their amplitudes with increasing subject age (primarily in P300) were also found to be significant. The amplitude of the motion-onset VEPs to radial motion remained the most constant parameter with increasing age. Age-related changes were stronger in males. Our results indicate that cognitive VEPs, despite larger variability of their parameters, could be a useful criterion for an objective evaluation of the aging processes within the CNS. Possible differences in aging between the motion-processing system and the form-processing system within the visual pathway might be indicated by the more pronounced delay in the motion-onset VEPs and by their preserved size for radial motion (a biologically significant variant of motion) compared to the changes in pattern-reversal VEPs. Copyright © 2012 Elsevier Ltd. All rights reserved.

Pattern Visual Evoked Potentials Elicited by Organic Electroluminescence Screen

PubMed Central

Matsumoto, Celso Soiti; Shinoda, Kei; Matsumoto, Harue; Funada, Hideaki; Minoda, Haruka

2014-01-01

Purpose. To determine whether organic electroluminescence (OLED) screens can be used as visual stimulators to elicit pattern-reversal visual evoked potentials (p-VEPs). Method. Checkerboard patterns were generated on a conventional cathode-ray tube (S710, Compaq Computer Co., USA) screen and on an OLED (17 inches, 320 × 230 mm, PVM-1741, Sony, Tokyo, Japan) screen. The time course of the luminance changes of each monitor was measured with a photodiode. The p-VEPs elicited by these two screens were recorded from 15 eyes of 9 healthy volunteers (22.0 ± 0.8 years). Results. The OLED screen had a constant time delay from the onset of the trigger signal to the start of the luminescence change. The delay during the reversal phase from black to white for the pattern was 1.0 msec on the cathode-ray tube (CRT) screen and 0.5 msec on the OLED screen. No significant differences in the amplitudes of P100 and the implicit times of N75 and P100 were observed in the p-VEPs elicited by the CRT and the OLED screens. Conclusion. The OLED screen can be used as a visual stimulator to elicit p-VEPs; however the time delay and the specific properties in the luminance change must be taken into account. PMID:25197652

The influence of deltalycyn and transcranial cerebellar stimulation upon recovery of retina after photo stress in patients with diabetic retinopathy.

PubMed

Kresyun, Nataliya Valentinivna

2014-01-01

The characteristics of visual evoked potentials (VEP) have been studied in diabetic patients with and without diabetic retinopathy. Magnetic impulses (2.0 T1 at the height of impulse) have been delivered to the cerebellar surface transcranially using the "Neuro-MS/D", (Russia Federation). Delta- sleep inducing peptide ("Deltalycyn", "Biopharma", Russia Federation) was intranasally delivered in 30 min before photostress. Afterwards VEP have been registered every 20 s from the moment of photo stress during one minute. An increase of the latency period and a reduction of the VEP amplitude have been recorded in the period following photo stress exposure of the macular part of the retina. The VEP characteristics restored to the initial level in 73.5 +/- 3.3 s from the photo stress moment in the control group; while in diabetic patients with retinopathy this index was 137.2 +/- 11.3 s. In the. presence of cerebellar transcranial magnetic stimulations (2.0 T1, 20 impulses) the VEP amplitude depression was less pro- nounced, and the restoration period of the VEP characteristics shortened to 110.3+ 12.7 s, while in deltalycyn treated patients restoration was observed in 95.1+ 6.8 s. Under condition of combined usage of deltalycyn and TMS period of restoration of VEP was shortened up to 82.5 +/- 6.5 s. Retinopathy development is linked to prolonged VEP latency period (P100), lowering of the N75-P100 amplitude, as well as to enlargement of the recovery period of the retina's functional capacity in patients suffering from the diabetes mellitus in the presence of photo stress. Superlatively administered deltalycyn and cerebellar transcranial magnetic stimulation facilitates a faster recovery of the retina's functional capacity in response to photo stress in diabetic patients with retinopathy. 3. Combined usage of deltalycyn and cerebellar transcranial stimulation caused the potentiated shortening of post-photo stress recovering of VEP in patients with diabetic retinopathy.

Basophil mediated pro-allergic inflammation in vehicle-emitted particles exposure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zakharenko, Alexander M.

Despite of the fact that engine manufacturers develop a new technology to reduce exhaust emissions, insufficient attention given to particulate emissions. However, diesel exhaust particles are a major source of air-borne pollution, contain vast amount of polycyclic aromatic hydrocarbons (PAHs) and may have deleterious effects on the immune system, resulting in the induction and enhancement of pro-allergic processes. In the current study, vehicle emitted particles (VEP) from 2 different types of cars (diesel - D and gasoline - G) and locomotive (L) were collected. Overall, 129 four-week-old, male SPF-class Kunming mice were subcutaneously instilled with either low dose 100, 250more » or high dose, 500 mg/kg VEP and 15 mice were assigned as control group. The systemic toxicity was evaluated and alterations in the percentages of the CD3, CD4, CD8, CD16, CD25 expressing cells, basophils, eosinophils and neutrophils were determined. Basophil percentages were inversely associated with the PAH content of the VEPs, however basophil sensitization was more important than cell count in VEP exposure. Thus, the effects of VEP-PAHs emerge with the activation of basophils in an allergen independent fashion. Despite the increased percentage of CD4+ T cells, a sharp decrease in basophil counts at 500 mg/kg of VEP indicates a decreased inhibitory effect of CD16+ monocytes on the proliferation of CD4+ T cell and suppressed polarization into a Th2 phenotype. Therefore, although the restrictions for vehicles emissions differ between countries, follow up studies and strict regulations are needed. - Highlights: • Basophil sensitization is more important than cell count in VEP exposure. • CD16+ cells are more effective than basophils on CD4+ T cell proliferation. • CD16+ and CD16- monocytes respond to VEP exposure in opposite directions. • CD8+ T cell proliferation is inhibited by all doses of VEPs. • Globally, more stringent standards are needed for vehicle particle emissions.« less

Evaluation of hemifield sector analysis protocol in multifocal visual evoked potential objective perimetry for the diagnosis and early detection of glaucomatous field defects.

PubMed

Mousa, Mohammad F; Cubbidge, Robert P; Al-Mansouri, Fatima; Bener, Abdulbari

2014-02-01

Multifocal visual evoked potential (mfVEP) is a newly introduced method used for objective visual field assessment. Several analysis protocols have been tested to identify early visual field losses in glaucoma patients using the mfVEP technique, some were successful in detection of field defects, which were comparable to the standard automated perimetry (SAP) visual field assessment, and others were not very informative and needed more adjustment and research work. In this study we implemented a novel analysis approach and evaluated its validity and whether it could be used effectively for early detection of visual field defects in glaucoma. Three groups were tested in this study; normal controls (38 eyes), glaucoma patients (36 eyes) and glaucoma suspect patients (38 eyes). All subjects had a two standard Humphrey field analyzer (HFA) test 24-2 and a single mfVEP test undertaken in one session. Analysis of the mfVEP results was done using the new analysis protocol; the hemifield sector analysis (HSA) protocol. Analysis of the HFA was done using the standard grading system. Analysis of mfVEP results showed that there was a statistically significant difference between the three groups in the mean signal to noise ratio (ANOVA test, p < 0.001 with a 95% confidence interval). The difference between superior and inferior hemispheres in all subjects were statistically significant in the glaucoma patient group in all 11 sectors (t-test, p < 0.001), partially significant in 5 / 11 (t-test, p < 0.01), and no statistical difference in most sectors of the normal group (1 / 11 sectors was significant, t-test, p < 0.9). Sensitivity and specificity of the HSA protocol in detecting glaucoma was 97% and 86%, respectively, and for glaucoma suspect patients the values were 89% and 79%, respectively. The new HSA protocol used in the mfVEP testing can be applied to detect glaucomatous visual field defects in both glaucoma and glaucoma suspect patients. Using this protocol can provide information about focal visual field differences across the horizontal midline, which can be utilized to differentiate between glaucoma and normal subjects. Sensitivity and specificity of the mfVEP test showed very promising results and correlated with other anatomical changes in glaucoma field loss.

The locus of color sensation: Cortical color loss and the chromatic visual evoked potential

PubMed Central

Crognale, Michael A.; Duncan, Chad S.; Shoenhard, Hannah; Peterson, Dwight J.; Berryhill, Marian E.

2013-01-01

Color losses of central origin (cerebral achromatopsia and dyschromatopsia) can result from cortical damage and are most commonly associated with stroke. Such cases have the potential to provide useful information regarding the loci of the generation of the percept of color. One available tool to examine this issue is the chromatic visual evoked potential (cVEP). The cVEP has been used successfully to objectively quantify losses in color vision capacity in both congenital and acquired deficiencies of retinal origin but has not yet been applied to cases of color losses of cortical origin. In addition, it is not known with certainty which cortical sites are responsible for the generation of the cVEP waveform components. Here we report psychophysical and electrophysiological examination of a patient with color deficits resulting from a bilateral cerebral infarct in the ventral occipitotemporal region. Although this patient demonstrated pronounced color losses of a general nature, the waveform of the cVEP remains unaffected. Contrast response functions of the cVEP are also normal for this patient. The results suggest that the percept of color arises after the origin of the cVEP and that normal activity in those areas that give rise to the characteristic negative wave of the cVEP are not sufficient to provide for the normal sensation of color. PMID:23986535

Impact of the Special Education Vocational Education Program (VEP) on Student Career Success

ERIC Educational Resources Information Center

Ofoegbu, Nelly E.; Azarmsa, Reza

2010-01-01

The Vocational Education Program (VEP) was established by the special education department in the Long Beach Unified School District (LBUSD) in an effort to assist students with disabilities to graduate from high school and be gainfully employed. This study investigated the impact of VEP on students' careers success after graduation. The…

Comparing multifocal VEP and standard automated perimetry in high-risk ocular hypertension and early glaucoma.

PubMed

Fortune, Brad; Demirel, Shaban; Zhang, Xian; Hood, Donald C; Patterson, Emily; Jamil, Annisa; Mansberger, Steven L; Cioffi, George A; Johnson, Chris A

2007-03-01

To compare the diagnostic performance of multifocal visual evoked potential (mfVEP) and standard automated perimetry (SAP), in eyes with high-risk ocular hypertension or early glaucoma. Both eyes of 185 individuals with high-risk ocular hypertension or early glaucoma were evaluated. Subjects ranged in age from 37 to 87 (mean +/- SD: 61 +/- 11 years). Pattern-reversal mfVEPs were obtained by using VERIS (Electro-Diagnostic Imaging, San Mateo, CA) with a four-electrode array and were analyzed with custom software. SAP visual fields (SITA-standard; Carl Zeiss Meditec, Inc., Dublin, CA) were obtained within 22.3 +/- 27.0 days of the mfVEP. Stereo disc photographs and Heidelberg Retina Tomograph (HRT) images were obtained during one visit, which was within 24.8 +/- 50.4 days of the mfVEP and 33.1 +/- 62.9 days of the SAP visual field. Abnormalities on the mfVEP were defined by using a variety of cluster criteria: SAP with pattern standard deviation (PSD) P

Usefulness of Intraoperative Monitoring of Visual Evoked Potentials in Transsphenoidal Surgery

PubMed Central

KAMIO, Yoshinobu; SAKAI, Naoto; SAMESHIMA, Tetsuro; TAKAHASHI, Goro; KOIZUMI, Shinichiro; SUGIYAMA, Kenji; NAMBA, Hiroki

2014-01-01

Postoperative visual outcome is a major concern in transsphenoidal surgery (TSS). Intraoperative visual evoked potential (VEP) monitoring has been reported to have little usefulness in predicting postoperative visual outcome. To re-evaluate its usefulness, we adapted a high-power light-stimulating device with electroretinography (ERG) to ascertain retinal light stimulation. Intraoperative VEP monitoring was conducted in TSSs in 33 consecutive patients with sellar and parasellar tumors under total venous anesthesia. The detectability rates of N75, P100, and N135 were 94.0%, 85.0%, and 79.0%, respectively. The mean latencies and amplitudes of N75, P100, and N135 were 76.8 ± 6.4 msec and 4.6 ± 1.8 μV, 98.0 ± 8.6 msec and 5.0 ± 3.4 μV, and 122.1 ± 16.3 msec and 5.7 ± 2.8 μV, respectively. The amplitude was defined as the voltage difference from N75 to P100 or P100 to N135. The criterion for amplitude changes was defined as a > 50% increase or 50% decrease in amplitude compared to the control level. The surgeon was immediately alerted when the VEP changed beyond these thresholds, and the surgical manipulations were stopped until the VEP recovered. Among the 28 cases with evaluable VEP recordings, the VEP amplitudes were stable in 23 cases and transiently decreased in 4 cases. In these 4 cases, no postoperative vision deterioration was observed. One patient, whose VEP amplitude decreased without subsequent recovery, developed vision deterioration. Intraoperative VEP monitoring with ERG to ascertain retinal light stimulation by the new stimulus device was reliable and feasible in preserving visual function in patients undergoing TSS. PMID:25070017

Policy uncertainty and corporate performance in government-sponsored voluntary environmental programs.

PubMed

Liu, Ning; Tang, Shui-Yan; Zhan, Xueyong; Lo, Carlos Wing-Hung

2018-08-01

This study combines insights from the policy uncertainty literature and neo-institutional theory to examine corporate performance in implementing a government-sponsored voluntary environmental program (VEP) during 2004-2012 in Guangzhou, China. In this regulatory context, characterized by rapid policy changes, corporate performance in VEPs is affected by government surveillance, policy uncertainty, and peer pressures. Specifically, if VEP participants have experienced more government surveillance, they tend to perform better in program implementation. Such positive influence of government surveillance is particularly evident among those joining under high and low, rather than moderate uncertainty. Participants also perform better if they belong to an industry with more certified VEP firms, but worse if they are located in a regulatory jurisdiction with more certified VEP firms. At a moderate level of policy uncertainty, within-industry imitation is most likely to occur but within-jurisdiction imitation is least likely to occur. Copyright © 2018 Elsevier Ltd. All rights reserved.

Color blindness among multiple sclerosis patients in Isfahan

PubMed Central

Shaygannejad, Vahid; Golabchi, Khodayar; Dehghani, Alireza; Ashtari, Fereshteh; Haghighi, Sepehr; Mirzendehdel, Mahsa; Ghasemi, Majid

2012-01-01

Background: Multiple sclerosis (MS) is a disease of young and middle aged individuals with a demyelinative axonal damage nature in central nervous system that causes various signs and symptoms. As color vision needs normal function of optic nerve and macula, it is proposed that MS can alter it via influencing optic nerve. In this survey, we evaluated color vision abnormalities and its relationship with history of optic neuritis and abnormal visual evoked potentials (VEPs) among MS patients. Materials and Methods: The case group was included of clinically definitive MS patients and the same number of normal population was enrolled as the control group. Color vision of all the participants was evaluated by Ishihara test and then visual evoked potential (VEPs) and history of optic neuritis (ON) was assessed among them. Then, frequency of color blindness was compared between the case and the control group. Finally, color blinded patients were compared to those with the history of ON and abnormal VEPs. Results: 63 MS patients and the same number of normal populations were enrolled in this study. 12 patients had color blindness based on the Ishihara test; only 3 of them were among the control group, which showed a significant different between the two groups (P = 0.013). There was a significant relationship between the color blindness and abnormal VEP (R = 0.53, P = 0.023) but not for the color blindness and ON (P = 0.67). Conclusions: This study demonstrates a significant correlation between color blindness and multiple sclerosis including ones with abnormal prolonged VEP latencies. Therefore, in individuals with acquired color vision impairment, an evaluation for potentially serious underlying diseases like MS is essential. PMID:23267377

Flash visual evoked potentials in patients with periventricular leucomalacia in children less than 1 year of age

PubMed Central

Jethani, Jitendra; Jethani, Monika

2013-01-01

Background and Aim: Children with periventricular leucomalacia (PVL) are known to have visual impairment of various forms starting from reduced vision, field defects, congnitive problems, and problems with hand eye coordination. There is very scant data/literature on the visual evoked potentials (VEPs) at an early age in children with PVL. We did a study to evaluate the flash visual evoked potentials (fVEPs) in children with PVL less than 1 year of age. Materials and Methods: A total of nine children diagnosed as having PVL on magnetic resonance imaging were included in the study. The mean age was 9.7± 3.5 months. All children underwent handheld fVEPs under sedation at two different flash frequencies 1.4 and 8 Hz. Results: The mean latency of N1 and P1 on stimulation with 1.4 Hz was 47.9± 15.2 and 77.7± 26.0 ms, respectively. However, on stimulation with 8 Hz the mean latency of N1 and P1 was 189.8± 25.6 and 238.4± 33.6 ms, respectively. The mean amplitude with 1.4 Hz and 8 stimulation frequency was 5.6± 4.5 and 5.59± 3 mV, respectively. Conclusion: We have found for the first time that there is a change in the latency and the delay occurs at 8 Hz frequency but not at 1.4 Hz. We also conclude that amplitudes by fVEPs may be normal even in presence of periventricular changes. The amplitudes of fVEPs are not reliable in children with PVL. PMID:24343595

Nerve fibre layer analysis with GDx with a variable corneal compensator in patients with multiple sclerosis.

PubMed

Della Mea, Giovanni; Bacchetti, Sonia; Zeppieri, Marco; Brusini, Paolo; Cutuli, Daniela; Gigli, Gian Luigi

2007-01-01

To evaluate the ability of GDx with variable corneal compensator (VCC) compared to visual-evoked potentials (VEPs) and standard automated perimetry (SAP) in the detection of early optic nerve damage in patients with multiple sclerosis (MS). 46 eyes of 23 MS patients were included. Ten of them had a history of acute retrobulbar optic neuritis. A control group of 20 normal subjects was also included. All subjects underwent a complete ophthalmological examination and testing with SAP, GDx VCC and VEPs. 19 eyes (41.3%) were abnormal with GDx VCC compared to 38 eyes (82.6%) with SAP and 31 (64.4%) with VEPs. In the optic neuritis group, 9 eyes (69.2%) had optic nerve pallor; SAP was abnormal in 8 of these eyes (61.5%) while VEPs and GDx VCC were abnormal in 6 eyes (46.1%). 2/20 eyes (10.0%) in the control group gave a false-positive abnormal result with SAP. GDx VCC and VEP were normal for all the eyes in the control group. GDx VCC is less able to detect early defects in MS patients compared to the currently used standard techniques of SAP and VEPs. Copyright (c) 2007 S. Karger AG, Basel.

An automated and fast approach to detect single-trial visual evoked potentials with application to brain-computer interface.

PubMed

Tu, Yiheng; Hung, Yeung Sam; Hu, Li; Huang, Gan; Hu, Yong; Zhang, Zhiguo

2014-12-01

This study aims (1) to develop an automated and fast approach for detecting visual evoked potentials (VEPs) in single trials and (2) to apply the single-trial VEP detection approach in designing a real-time and high-performance brain-computer interface (BCI) system. The single-trial VEP detection approach uses common spatial pattern (CSP) as a spatial filter and wavelet filtering (WF) a temporal-spectral filter to jointly enhance the signal-to-noise ratio (SNR) of single-trial VEPs. The performance of the joint spatial-temporal-spectral filtering approach was assessed in a four-command VEP-based BCI system. The offline classification accuracy of the BCI system was significantly improved from 67.6±12.5% (raw data) to 97.3±2.1% (data filtered by CSP and WF). The proposed approach was successfully implemented in an online BCI system, where subjects could make 20 decisions in one minute with classification accuracy of 90%. The proposed single-trial detection approach is able to obtain robust and reliable VEP waveform in an automatic and fast way and it is applicable in VEP based online BCI systems. This approach provides a real-time and automated solution for single-trial detection of evoked potentials or event-related potentials (EPs/ERPs) in various paradigms, which could benefit many applications such as BCI and intraoperative monitoring. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

The dynamic allocation of attention to emotion: simultaneous and independent evidence from the late positive potential and steady state visual evoked potentials.

PubMed

Hajcak, Greg; MacNamara, Annmarie; Foti, Dan; Ferri, Jamie; Keil, Andreas

2013-03-01

Emotional stimuli capture and hold attention without explicit instruction. The late positive potential (LPP) component of the event related potential can be used to track motivated attention toward emotional stimuli, and is larger for emotional compared to neutral pictures. In the frequency domain, the steady state visual evoked potential (ssVEP) has also been used to track attention to stimuli flickering at a particular frequency. Like the LPP, the ssVEP is also larger for emotional compared to neutral pictures. Prior work suggests that both the LPP and ssVEP are sensitive to "top-down" manipulations of attention, however the LPP and ssVEP have not previously been examined using the same attentional manipulation in the same participants. In the present study, LPP and ssVEP amplitudes were simultaneously elicited by unpleasant and neutral pictures. Partway through picture presentation, participants' attention was directed toward an arousing or non-arousing region of unpleasant pictures. In line with prior work, the LPP was reduced when attention was directed toward non-arousing compared to arousing regions of unpleasant pictures; similar results were observed for the ssVEP. Thus, both electrocortical measures index affective salience and are sensitive to directed (here: spatial) attention. Variation in the LPP and ssVEP was unrelated, suggesting that these measures are not redundant with each other and may capture different neurophysiological aspects of affective stimulus processing and attention. Copyright © 2011 Elsevier B.V. All rights reserved.

Improvement in conduction velocity after optic neuritis measured with the multifocal VEP.

PubMed

Yang, E Bo; Hood, Donald C; Rodarte, Chris; Zhang, Xian; Odel, Jeffrey G; Behrens, Myles M

2007-02-01

To test the efficacy of the multifocal visual evoked potential (mfVEP) technique after long-term latency changes in optic neuritis (ON)/multiple sclerosis (MS), mfVEPs were recorded in 12 patients with ON/MS. Sixty local VEP responses were recorded simultaneously. mfVEP was recorded from both eyes of 12 patients with ON/MS. Patients were tested twice after recovery from acute ON episodes, which occurred in 14 of the 24 eyes. After recovery, all eyes had 20/20 or better visual acuity and normal visual fields as measured with static automated perimetry (SAP). The time between the two postrecovery tests varied from 6 to 56 months. Between test days, the visual fields obtained with SAP remained normal. Ten of the 14 affected eyes showed improvement in median latency on the mfVEP. Six of these eyes fell at or below (improved latency) the 96% confidence interval for the control eyes. None of the 10 initially unaffected eyes fell below the 96% lower limit. Although the improvement was widespread across the field, it did not include all regions. For the six eyes showing clear improvement, on average, 78% of the points had latencies that were shorter on test 2 than on test 1. A substantial percentage of ON/MS patients show a long-term improvement in conduction velocity. Because this improvement can be local, the mfVEP should allow these improvements to be monitored in patients with ON/MS.

Visually Evoked Potentials after Panretinal Photocoagulation in Omani Patients with Uncontrolled Diabetes Mellitus

PubMed Central

Shenoy, Radha; Al-Belushi, Habiba; Al-Ajmi, Sadiqa; Al-Nabhani, Susan Margaret; Ganguly, Shyam Sunder; Bialasiewicz, Alexander A.

2008-01-01

Aim: To report on the changes of latency and amplitudes of the pattern VEP in patients with uncontrolled diabetes mellitus II and I before and after panretinal laser treatment. Design: Single center hospital based comparative study. Methods: One hundred eyes of patients with proliferative diabetic vitreoretinopathy, and HbA1C ≥ 10 percent were subjected to Pattern Visually Evoked Potentials (Medtronic keyopint system, Nicolet) prior to and 4 weeks after PRP. Results were compared to age-matched non-diabetic controls. Chi-Square test, and paired ‘t’ test were used for statistical analysis. Results: Preoperative mean VEP amplitude was 8.35mV±3.71, and not significantly different to the control group (mean 10.51mV±3.34) (chi square test p=1). Mean preoperative P100 latency was 106.93±7.90ms and significantly different to the control group (103.21±7.65ms) (paired t-test p=0.001). After laser treatment, VEP amplitudes decreased in 48/100 eyes (mean total 5.11mV±2.4), and P100 latency increased in 75/100 eyes (mean total 110.47±7.35ms). Conclusion: In this study, PRP was followed by a significant decrease in VEP amplitudes in 48 percent and increase in latency in 75 percent of eyes. PMID:21346837

The effects of luminance contribution from large fields to chromatic visual evoked potentials.

PubMed

Skiba, Rafal M; Duncan, Chad S; Crognale, Michael A

2014-02-01

Though useful from a clinical and practical standpoint uniform, large-field chromatic stimuli are likely to contain luminance contributions from retinal inhomogeneities. Such contribution can significantly influence psychophysical thresholds. However, the degree to which small luminance artifacts influence the chromatic VEP has been debated. In particular, claims have been made that band-pass tuning observed in chromatic VEPs result from luminance intrusion. However, there has been no direct evidence presented to support these claims. Recently, large-field isoluminant stimuli have been developed to control for intrusion from retinal inhomogeneities with particular regard to the influence of macular pigment. We report here the application of an improved version of these full-field stimuli to directly test the influence of luminance intrusion on the temporal tuning of the chromatic VEP. Our results show that band-pass tuning persists even when isoluminance is achieved throughout the extent of the stimulus. In addition, small amounts of luminance intrusion affect neither the shape of the temporal tuning function nor the major components of the VEP. These results support the conclusion that the chromatic VEP can depart substantially from threshold psychophysics with regard to temporal tuning and that obtaining a low-pass function is not requisite evidence of selective chromatic activation in the VEP. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Effectiveness of a Vocational Enablement Protocol for Employees With Hearing Difficulties

PubMed Central

Gussenhoven, Arjenne H. M.; Anema, Johannes R.; Witte, Birgit I.; Goverts, S. Theo

2017-01-01

The aim of this study was to evaluate the effectiveness of a vocational enablement protocol (VEP) on need for recovery (NFR) after work as compared with usual care for employees with hearing difficulties. In a randomized controlled trial design, 136 employees with hearing impairment were randomly assigned to either the VEP or the control group. VEP is a multidisciplinary program integrating audiological and occupational care for individuals experiencing difficulties in the workplace due to hearing loss. The primary outcome measure was NFR. Secondary outcome measures were communication strategy subscales (e.g., self-acceptance and maladaptive behavior), distress, and self-efficacy. Data were collected using questionnaires at baseline and at 3, 6, 9, and 12 months follow-up. No significant difference over the complete follow-up period was found between the intervention and control group for NFR. However, we observed a significant difference for one of the secondary outcomes after 12 months. “Self-acceptance” increased significantly in the VEP group, compared with the controls. The mean difference between the two groups was small, being only 0.24 (95% CI [0.04, 0.44]) on a scale of 1 to 5. The results do not support the use of VEP if the aim is to reduce NFR after work at 12 months follow-up. It may be that NFR does not adequately capture what is covered in the VEP. Although marginal, the effect on self-acceptance was significant. This is encouraging given that positive effects on self-acceptance have rarely been shown for audiological rehabilitation programs. Suggestions for further improvement of the VEP are discussed. PMID:29298599

Neural coding of image structure and contrast polarity of Cartesian, hyperbolic, and polar gratings in the primary and secondary visual cortex of the tree shrew.

PubMed

Poirot, Jordan; De Luna, Paolo; Rainer, Gregor

2016-04-01

We comprehensively characterize spiking and visual evoked potential (VEP) activity in tree shrew V1 and V2 using Cartesian, hyperbolic, and polar gratings. Neural selectivity to structure of Cartesian gratings was higher than other grating classes in both visual areas. From V1 to V2, structure selectivity of spiking activity increased, whereas corresponding VEP values tended to decrease, suggesting that single-neuron coding of Cartesian grating attributes improved while the cortical columnar organization of these neurons became less precise from V1 to V2. We observed that neurons in V2 generally exhibited similar selectivity for polar and Cartesian gratings, suggesting that structure of polar-like stimuli might be encoded as early as in V2. This hypothesis is supported by the preference shift from V1 to V2 toward polar gratings of higher spatial frequency, consistent with the notion that V2 neurons encode visual scene borders and contours. Neural sensitivity to modulations of polarity of hyperbolic gratings was highest among all grating classes and closely related to the visual receptive field (RF) organization of ON- and OFF-dominated subregions. We show that spatial RF reconstructions depend strongly on grating class, suggesting that intracortical contributions to RF structure are strongest for Cartesian and polar gratings. Hyperbolic gratings tend to recruit least cortical elaboration such that the RF maps are similar to those generated by sparse noise, which most closely approximate feedforward inputs. Our findings complement previous literature in primates, rodents, and carnivores and highlight novel aspects of shape representation and coding occurring in mammalian early visual cortex. Copyright © 2016 the American Physiological Society.

Enhancing Performance and Bit Rates in a Brain-Computer Interface System With Phase-to-Amplitude Cross-Frequency Coupling: Evidences From Traditional c-VEP, Fast c-VEP, and SSVEP Designs.

PubMed

Dimitriadis, Stavros I; Marimpis, Avraam D

2018-01-01

A brain-computer interface (BCI) is a channel of communication that transforms brain activity into specific commands for manipulating a personal computer or other home or electrical devices. In other words, a BCI is an alternative way of interacting with the environment by using brain activity instead of muscles and nerves. For that reason, BCI systems are of high clinical value for targeted populations suffering from neurological disorders. In this paper, we present a new processing approach in three publicly available BCI data sets: (a) a well-known multi-class ( N = 6) coded-modulated Visual Evoked potential (c-VEP)-based BCI system for able-bodied and disabled subjects; (b) a multi-class ( N = 32) c-VEP with slow and fast stimulus representation; and (c) a steady-state Visual Evoked potential (SSVEP) multi-class ( N = 5) flickering BCI system. Estimating cross-frequency coupling (CFC) and namely δ-θ [δ: (0.5-4 Hz), θ: (4-8 Hz)] phase-to-amplitude coupling (PAC) within sensor and across experimental time, we succeeded in achieving high classification accuracy and Information Transfer Rates (ITR) in the three data sets. Our approach outperformed the originally presented ITR on the three data sets. The bit rates obtained for both the disabled and able-bodied subjects reached the fastest reported level of 324 bits/min with the PAC estimator. Additionally, our approach outperformed alternative signal features such as the relative power (29.73 bits/min) and raw time series analysis (24.93 bits/min) and also the original reported bit rates of 10-25 bits/min . In the second data set, we succeeded in achieving an average ITR of 124.40 ± 11.68 for the slow 60 Hz and an average ITR of 233.99 ± 15.75 for the fast 120 Hz. In the third data set, we succeeded in achieving an average ITR of 106.44 ± 8.94. Current methodology outperforms any previous methodologies applied to each of the three free available BCI datasets.

An Extended Proof-Carrying Code Framework for Security Enforcement

NASA Astrophysics Data System (ADS)

Pirzadeh, Heidar; Dubé, Danny; Hamou-Lhadj, Abdelwahab

The rapid growth of the Internet has resulted in increased attention to security to protect users from being victims of security threats. In this paper, we focus on security mechanisms that are based on Proof-Carrying Code (PCC) techniques. In a PCC system, a code producer sends a code along with its safety proof to the consumer. The consumer executes the code only if the proof is valid. Although PCC has been shown to be a useful security framework, it suffers from the sheer size of typical proofs -proofs of even small programs can be considerably large. In this paper, we propose an extended PCC framework (EPCC) in which, instead of the proof, a proof generator for the program in question is transmitted. This framework enables the execution of the proof generator and the recovery of the proof on the consumer's side in a secure manner using a newly created virtual machine called the VEP (Virtual Machine for Extended PCC).

The effect of spectral filters on VEP and alpha-wave responses.

PubMed

Willeford, Kevin T; Fimreite, Vanessa; Ciuffreda, Kenneth J

2016-01-01

Spectral filters are used to treat light sensitivity in individuals with traumatic brain injury (TBI); however, the effect of these filters on normal visual function has not been elucidated. Thus, the current study aimed to determine the effect of spectral filters on objectively-measured visual-evoked potential (VEP) and alpha-wave responses in the visually-normal population. The full-field (15°H×17°V), pattern-reversal VEP (20' check size, mean luminance 52cd/m(2)) was administered to 20 visually-normal individuals. They were tested with four Intuitive-Colorimeter-derived, broad-band, spectral filters (i.e., gray/neutral density, blue, yellow, and red), which produced similar luminance values for the test stimulus. The VEP N75 and P100 latencies, and VEP amplitude, were recorded. Power spectrum analysis was used to derive the respective powers at each frequency, and peak frequency, for the selected 9-11Hz components of the alpha band. Both N75 and P100 latencies increased with the addition of each filter when compared to baseline. Additionally, each filter numerically reduced intra-session amplitude variability relative to baseline. There were no significant effects on either the mean VEP amplitude or alpha wave parameters. The Intuitive Colorimeter filters significantly increased both N75 and P100 latencies, an effect which is primarily attributable (∼75%) to luminance, and in some cases, specific spectral effects (e.g., blue and red). VEP amplitude and alpha power were not significantly affected. These findings provide an important reference to which either amplitude or power changes in light-sensitive, younger clinical groups can be compared. Copyright © 2015 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

Contributing factors to VEP grating acuity deficit and inter-ocular acuity difference in children with cerebral visual impairment.

PubMed

Cavascan, Nívea Nunes; Salomão, Solange Rios; Sacai, Paula Yuri; Pereira, Josenilson Martins; Rocha, Daniel Martins; Berezovsky, Adriana

2014-04-01

To investigate contributing factors to visual evoked potential (VEP) grating acuity deficit (GAD) and inter-ocular acuity difference (IAD) measured by sweep-VEPs in children with cerebral visual impairment (CVI). VEP GAD was calculated for the better acuity eye by subtracting acuity thresholds from mean normal VEP grating acuity according to norms from our own laboratory. Deficits were categorized as mild (0.17 ≤ deficit < 0.40 log units), moderate (0.40 ≤ deficit < 0.70 log units) or severe (deficit ≥0.70 log units). Maximum acceptable IAD was 0.10 log units. A group of 115 children (66 males-57 %) with ages ranging from 1.2 to 166.5 months (median = 17.7) was examined. VEP GAD ranged from 0.17 to 1.28 log units (mean = 0.68 ± 0.27; median = 0.71), and it was mild in 23 (20 %) children, moderate in 32 (28 %) and severe in 60 (52 %). Severe deficit was significantly associated with older age and anti-seizure drug therapy. IAD ranged from 0 to 0.49 log units (mean = 0.06 ± 0.08; median = 0.04) and was acceptable in 96 (83 %) children. Children with strabismus and nystagmus had IAD significantly larger compared to children with orthoposition. In a large cohort of children with CVI, variable severity of VEP GAD was found, with more than half of the children with severe deficits. Older children and those under anti-seizure therapy were at higher risk for larger deficits. Strabismus and nystagmus provided larger IADs. These results should be taken into account on the clinical management of children with this leading cause of bilateral visual impairment.

The effects of retinal abnormalities on the multifocal visual evoked potential.

PubMed

Chen, John Y; Hood, Donald C; Odel, Jeffrey G; Behrens, Myles M

2006-10-01

To examine the effects on the amplitude and latency of the multifocal visual evoked potential (mfVEP) in retinal diseases associated with depressed multifocal electroretinograms (mfERG). Static automated perimetry (SAP), mfERGs, and mfVEPs were obtained from 15 individuals seen by neuro-ophthalmologists and diagnosed with retinal disease based on funduscopic examination, visual field, and mfERG. Optic neuropathy was ruled out in all cases. Diagnoses included autoimmune retinopathy (n = 3), branch retinal arterial occlusion (n = 3), branch retinal vein occlusion (n = 1), vitamin A deficiency (n = 1), digoxin/age-related macular degeneration (n = 1), multiple evanescent white dot syndrome (n = 1), and nonspecific retinal disease (n = 5). Patients were selected from a larger group based on abnormal mfERG amplitudes covering a diameter of 20 degrees or greater. Fourteen (93%) of 15 patients showed significant mfVEP delays, as determined by either mean latency or the probability of a cluster of delayed local responses. Thirteen of 15 patients had normal mfVEP amplitudes in regions corresponding to markedly reduced or nonrecordable mfERG responses. These findings can be mimicked in normal individuals by viewing the display through a neutral-density filter. Retinal diseases can result in mfVEPs of relatively normal amplitudes, often with delays, in regions showing decreased mfERG responses and visual field sensitivity loss. Consequently, a retinal problem can be missed, or dismissed as functional, if a diagnosis is based on an mfVEP of normal or near-normal amplitude. Further, in patients with marked mfVEP delays, a retinal problem could be confused with optic neuritis, especially in a patient with a normal appearing fundus.

Multifocal Visual Evoked Potential in Eyes With Temporal Hemianopia From Chiasmal Compression: Correlation With Standard Automated Perimetry and OCT Findings.

PubMed

Sousa, Rafael M; Oyamada, Maria K; Cunha, Leonardo P; Monteiro, Mário L R

2017-09-01

To verify whether multifocal visual evoked potential (mfVEP) can differentiate eyes with temporal hemianopia due to chiasmal compression from healthy controls. To assess the relationship between mfVEP, standard automated perimetry (SAP), and Fourier domain-optical coherence tomography (FD-OCT) macular and peripapillary retinal nerve fiber layer (RNFL) thickness measurements. Twenty-seven eyes with permanent temporal visual field (VF) defects from chiasmal compression on SAP and 43 eyes of healthy controls were submitted to mfVEP and FD-OCT scanning. Multifocal visual evoked potential was elicited using a stimulus pattern of 60 sectors and the responses were averaged for the four quadrants and two hemifields. Optical coherence tomography macular measurements were averaged in quadrants and halves, while peripapillary RNFL thickness was averaged in four sectors around the disc. Visual field loss was estimated in four quadrants and each half of the 24-2 strategy test points. Multifocal visual evoked potential measurements in the two groups were compared using generalized estimated equations, and the correlations between mfVEP, VF, and OCT findings were quantified. Multifocal visual evoked potential-measured temporal P1 and N2 amplitudes were significantly smaller in patients than in controls. No significant difference in amplitude was observed for nasal parameters. A significant correlation was found between mfVEP amplitudes and temporal VF loss, and between mfVEP amplitudes and the corresponding OCT-measured macular and RNFL thickness parameters. Multifocal visual evoked potential amplitude parameters were able to differentiate eyes with temporal hemianopia from controls and were significantly correlated with VF and OCT findings, suggesting mfVEP is a useful tool for the detection of visual abnormalities in patients with chiasmal compression.

Sensitivity of visual evoked potentials and spectral domain optical coherence tomography in early relapsing remitting multiple sclerosis.

PubMed

Behbehani, Raed; Ahmed, Samar; Al-Hashel, Jasem; Rousseff, Rossen T; Alroughani, Raed

2017-02-01

Visual evoked potentials and spectral-domain optical coherence tomography are common ancillary studies that assess the visual pathways from a functional and structural aspect, respectively. To compare prevalence of abnormalities of Visual evoked potentials (VEP) and spectral-domain optical coherence tomography (SDOCT) in patients with relapsing remitting multiple sclerosis (RRMS). A cross-sectional study of 100 eyes with disease duration of less than 5 years since the diagnosis. Correlation between retinal nerve fiber layer and ganglion-cell/inner plexiform layer with pattern-reversal visual evoked potentials amplitude and latency and contrast sensitivity was performed. The prevalence of abnormalities in pattern-reversal visual VEP was 56% while that of SOCT was 48% in all eyes. There was significant negative correlations between the average RNFL (r=-0.34, p=0.001) and GCIPL (r=-0.39, p<0.001) with VEP latency. In eyes with prior optic neuritis, a significant negative correlation was seen between average RNFL (r=-0.33, p=0.037) and GCIPL (r=-0.40, p=0.010) with VEP latency. We have found higher prevalence of VEP abnormalities than SCOCT in early relapsing-remitting multiple sclerosis. This suggests that VEP has a higher sensitivity for detecting lesions of the visual pathway in patients with early RRMS. Copyright © 2016 Elsevier B.V. All rights reserved.

Chromatic VEP in children with congenital colour vision deficiency.

PubMed

Tekavčič Pompe, Manca; Stirn Kranjc, Branka; Brecelj, Jelka

2010-09-01

Visual evoked potentials to chromatic stimulus (cVEP) are believed to selectively test the parvocellular visual pathway which is responsible for processing information about colour. The aim was to evaluate cVEP in children with red-green congenital colour vision deficiency. VEP responses of 15 colour deficient children were compared to 31 children with normal colour vision. An isoluminant red-green stimulus composed of horizontal gratings was presented in an onset-offset manner. The shape of the waveform was studied, as well as the latency and amplitude of positive (P) and negative (N) waves. cVEP response did not change much with increased age in colour deficient children, whereas normative data showed changes from a predominantly positive to a negative response with increased age. A P wave was present in 87% of colour deficient children (and in 100% of children with normal colour vision), whereas the N wave was absent in a great majority of colour deficient children and was present in 80% of children with normal colour vision. Therefore, the amplitude of the whole response (N-P) decreased linearly with age in colour deficient children, whereas in children with normal colour vision it increased linearly. P wave latency shortened with increased age in both groups. cVEP responses differ in children with congenital colour vision deficiency compared to children with normal colour vision. © 2010 The Authors, Ophthalmic and Physiological Optics © 2010 The College of Optometrists.

Pattern visual evoked potentials in eyes with disc swelling due to cat scratch disease-associated neuroretinitis.

PubMed

Chai, Yuzhu; Yamamoto, Shuichi; Hirayama, Atsuko; Yotsukura, Jiro; Yamazaki, Hiroko

2005-01-01

To evaluate optic nerve function by pattern visual evoked potentials (VEPs) in eyes with optic disc swelling due to neuroretinitis associated with cat scratch disease (CSD). Four eyes of four patients with marked optic disc swelling resembling optic neuritis but diagnosed serologically as CSD received systemic steroid treatment. VEPs elicited by black and white checkerboard stimuli created on a TV monitor were recorded before the treatment. The visual acuity (VA) in the affected eyes was decreased to 20/50 in two eyes and finger counting in two eyes at their initial visits. Ophthalmoscopic examination revealed neuroretinitis characterized by severe optic disc swelling, chorioretinal exudates, and macular edema in all eyes. Anti-Bartonella henselae serum antibody was markedly elevated in all patients confirming the diagnosis of CSD. The P100 of the transient VEPs was only mildly reduced without a delay in the implicit times in three eyes and only slightly delayed in the other eye. The steady-state VEPs were mildly reduced in two eyes and phase-reversed in other two eyes. The VA fully recovered after systemic steroid treatment in all patients. Although all examined patients showed marked swelling of the optic disc and visual decrease, the pattern VEPs were not affected as severely as in idiopathic optic neuritis. However, the degree of change of the pattern VEPs varied among patients.

Normal versus High Tension Glaucoma: A Comparison of Functional and Structural Defects

PubMed Central

Thonginnetra, Oraorn; Greenstein, Vivienne C.; Chu, David; Liebmann, Jeffrey M.; Ritch, Robert; Hood, Donald C.

2009-01-01

Purpose To compare visual field defects obtained with both multifocal visual evoked potential (mfVEP) and Humphrey visual field (HVF) techniques to topographic optic disc measurements in patients with normal tension glaucoma (NTG) and high tension glaucoma (HTG). Methods We studied 32 patients with NTG and 32 with HTG. All patients had reliable 24-2 HVFs with a mean deviation (MD) of −10 dB or better, a glaucomatous optic disc and an abnormal HVF in at least one eye. Multifocal VEPs were obtained from each eye and probability plots created. The mfVEP and HVF probability plots were divided into a central 10-degree (radius) and an outer arcuate subfield in both superior and inferior hemifields. Cluster analyses and counts of abnormal points were performed in each subfield. Optic disc images were obtained with the Heidelberg Retina Tomograph III (HRT III). Eleven stereometric parameters were calculated. Moorfields regression analysis (MRA) and the glaucoma probability score (GPS) were performed. Results There were no significant differences in MD and PSD values between NTG and HTG eyes. However, NTG eyes had a higher percentage of abnormal test points and clusters of abnormal points in the central subfields on both mfVEP and HVF than HTG eyes. For HRT III, there were no significant differences in the 11 stereometric parameters or in the MRA and GPS analyses of the optic disc images. Conclusions The visual field data suggest more localized and central defects for NTG than HTG. PMID:19223786

Cortical functional correlates of responsiveness to short-lasting preventive intervention with ketogenic diet in migraine: a multimodal evoked potentials study.

PubMed

Di Lorenzo, Cherubino; Coppola, Gianluca; Bracaglia, Martina; Di Lenola, Davide; Evangelista, Maurizio; Sirianni, Giulio; Rossi, Paolo; Di Lorenzo, Giorgio; Serrao, Mariano; Parisi, Vincenzo; Pierelli, Francesco

2016-01-01

Here, we aim to identify cortical electrofunctional correlates of responsiveness to short-lasting preventiveintervention with ketogenic diet (KD) in migraine. Eighteen interictal migraineurs underwent visual (VEPs) and median nerve somatosensory (SSEPs) evokedpotentials before and after 1 month of KD during ketogenesis. We measured VEPs N1-P1 and SSEPs N20-P25 amplitudes respectively in six and in two sequential blocks of 100 sweeps as well as habituation as theslope of the linear regression between block 1 to 6 for VEPs or between 1 to 2 for SSEPs. After 1-month of KD, a significant reduction in the mean attack frequency and duration was observed (all P< 0.001). The KD did not change the 1st SSEP and VEP block of responses, but significantly inducednormalization of the interictally reduced VEPs and SSEPs (all p < 0.01) habituation during the subsequentblocks. KD could restore normal EPs habituation curves during stimulus repetition without significantly changing theearly amplitude responses. Thus, we hypothesize that KD acts on habituation regulating the balancebetween excitation and inhibition at the cortical level.

Dynamics of chromatic visual system processing differ in complexity between children and adults.

PubMed

Boon, Mei Ying; Suttle, Catherine M; Henry, Bruce I; Dain, Stephen J

2009-06-30

Measures of chromatic contrast sensitivity in children are lower than those of adults. This may be related to immaturities in signal processing at or near threshold. We have found that children's VEPs in response to low contrast supra-threshold chromatic stimuli are more intra-individually variable than those recorded from adults. Here, we report on linear and nonlinear analyses of chromatic VEPs recorded from children and adults. Two measures of signal-to-noise ratio are similar between the adults and children, suggesting that relatively high noise is unlikely to account for the poor clarity of negative and positive peak components in the children's VEPs. Nonlinear analysis indicates higher complexity of adults' than children's chromatic VEPs, at levels of chromatic contrast around and well above threshold.

Visual evoked potentials in patients after methanol poisoning.

PubMed

Urban, Pavel; Zakharov, Sergey; Diblík, Pavel; Pelclová, Daniela; Ridzoň, Petr

2016-01-01

We report the results of the visual evoked potentials (VEP) examination in patients after severe poisoning by methanol. The group of 47 patients (38 males and 9 females) was assembled out of persons who survived an outbreak of poisoning by the methanol adulterated alcohol beverages, which happened in the Czech Republic in 2012-2013. The visual evoked potentials examination was performed using monocular checkerboard pattern-reversal stimulation. Two criteria of abnormality were chosen: missing evoked response, and wave P1 latency > 117 ms. Non-parametric statistical methods (median, range, and the median test) were used to analyze factors influencing the VEP abnormality. The visual evoked potential was abnormal in 20 patients (43%), 5 of them had normal visual acuity on the Snellen chart. The VEP abnormality did not correlate significantly with initial serum concentrations of methanol, formic acid or lactate; however, it showed statistically significant inverse relation to the initial serum pH: the subgroup with the abnormal VEP had significantly lower median pH in comparison with the subgroup with the normal VEP (7.16 vs. 7.34, p = 0.04). The abnormality was not related to chronic alcohol abuse. The visual evoked potentials examination appeared sensitive enough to detected even subclinical impairment of the optic system. Metabolic acidosis is likely to be the key factor related to the development of visual damage induced by methanol. The examination performed with a delay of 1-9 months after the poisoning documented the situation relatively early after the event. It is considered as a baseline for the planned long-term follow-up of the patients, which will make it possible to assess the dynamics of the observed changes, their reversibility, and the occurrence of potential late sequelae. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

Multiple Frequency Contrast Source Inversion Method for Vertical Electromagnetic Profiling: 2D Simulation Results and Analyses

NASA Astrophysics Data System (ADS)

Li, Jinghe; Song, Linping; Liu, Qing Huo

2016-02-01

A simultaneous multiple frequency contrast source inversion (CSI) method is applied to reconstructing hydrocarbon reservoir targets in a complex multilayered medium in two dimensions. It simulates the effects of a salt dome sedimentary formation in the context of reservoir monitoring. In this method, the stabilized biconjugate-gradient fast Fourier transform (BCGS-FFT) algorithm is applied as a fast solver for the 2D volume integral equation for the forward computation. The inversion technique with CSI combines the efficient FFT algorithm to speed up the matrix-vector multiplication and the stable convergence of the simultaneous multiple frequency CSI in the iteration process. As a result, this method is capable of making quantitative conductivity image reconstruction effectively for large-scale electromagnetic oil exploration problems, including the vertical electromagnetic profiling (VEP) survey investigated here. A number of numerical examples have been demonstrated to validate the effectiveness and capacity of the simultaneous multiple frequency CSI method for a limited array view in VEP.

Ad-hoc and context-dependent adjustments of selective attention in conflict control: an ERP study with visual probes.

PubMed

Nigbur, R; Schneider, J; Sommer, W; Dimigen, O; Stürmer, B

2015-02-15

Cognitive conflict control in flanker tasks has often been described using the zoom-lens metaphor of selective attention. However, whether and how selective attention - in terms of suppression and enhancement - operates in this context has remained unclear. To examine the dynamic interplay of selective attention and cognitive control we used electrophysiological measures and presented task-irrelevant visual probe stimuli at foveal, parafoveal, and peripheral display positions. Target-flanker congruency varied either randomly from trial to trial (mixed-block) or block-wise (fixed-block) in order to induce reactive versus proactive control modes, respectively. Three EEG measures were used to capture ad-hoc adjustments within trials as well as effects of context-based predictions: the N1 component of the visual evoked potential (VEP) to probes, the VEP to targets, and the conflict-related midfrontal N2 component. Results from probe-VEPs indicate that enhanced processing of the foveal target rather than suppression of the peripheral flankers supports interference control. In incongruent mixed-block trials VEPs were larger to probes near the targets. In the fixed-blocks probe-VEPs were not modulated, but contrary to the mixed-block the preceding target-related VEP was affected by congruency. Results of the control-related N2 reveal largest amplitudes in the unpredictable context, which did not differentiate for stimulus and response incongruency. In contrast, in the predictable context, N2 amplitudes were reduced overall and differentiated between stimulus and response incongruency. Taken together these results imply that predictability alters interference control by a reconfiguration of stimulus processing. During unpredictable sequences participants adjust their attentional focus dynamically on a trial-by-trial basis as reflected in congruency-dependent probe-VEP-modulation. This reactive control mode also elicits larger N2 amplitudes. In contrast, when task demands are predictable, participants focus selective attention earlier as reflected in the target-related VEPs. This proactive control mode leads to smaller N2 amplitudes and absent probe effects. Copyright © 2014 Elsevier Inc. All rights reserved.

A practical VEP-based brain-computer interface.

PubMed

Wang, Yijun; Wang, Ruiping; Gao, Xiaorong; Hong, Bo; Gao, Shangkai

2006-06-01

This paper introduces the development of a practical brain-computer interface at Tsinghua University. The system uses frequency-coded steady-state visual evoked potentials to determine the gaze direction of the user. To ensure more universal applicability of the system, approaches for reducing user variation on system performance have been proposed. The information transfer rate (ITR) has been evaluated both in the laboratory and at the Rehabilitation Center of China, respectively. The system has been proved to be applicable to > 90% of people with a high ITR in living environments.

Surgical decompression in endocrine orbitopathy. Visual evoked potential evaluation and effect on the optic nerve.

PubMed

Clauser, Luigi C; Tieghi, Riccardo; Galie', Manlio; Franco, Filippo; Carinci, Francesco

2012-10-01

Endocrine orbitopathy (EO) represents the most frequent and important extrathyroidal stigma of Graves disease. This chronic autoimmune condition involves the orbital contents, including extraocular muscles, periorbital connective-fatty tissue and lacrimal gland. The increase of fat tissue and the enlargement of extraocular muscles within the bony confines of the orbit leads to proptosis, and in the most severe cases optic neuropathy, caused by compression and stretching of the optic nerve. The congestion and the pressure of the enlarged muscles, constrict the nerve and can lead to reduced sight or loss of vision with the so called "orbital apex syndrome". Generally surgical treatment of EO, based on fat and/or orbital wall expansion, is possible and effective in improving exophthalmos and diplopia. Since there are limited reports focussing on optic neuropathy recovery after fat and/or orbital walls decompression the Authors decided to perform a retrospective analysis on a series of patients affected by EO. The study population was composed of 10 patients affected by EO and presenting to the Unit of Cranio Maxillofacial Surgery, Center for Craniofacial Deformities & Orbital Surgery St. Anna Hospital and University, Ferrara, Italy, for evaluation and treatment. A complete Visual Evoked Potentials (VEP) evaluation was performed. There were seven women and three men with a median age of 55 years. Optic nerve VEP amplitude and latency were recorded as normal or pathological. Abnormal results were scored as moderate, mild and severe. Differences in VEP pre and post-operatively were recorded as present or absent (i.e. VEP Delta). Pearson chi square test was applied. There were 20 operated orbits. The first VEP evaluation was performed 3.2 months before surgery and post-operative VEP control was done after a mean of 18.7 months. Fat decompression was performed in all cases and eight patients had also bony decompression. VEP amplitude and latency were affected in 10 and 15 cases before operation and six and nine after surgery, respectively. VEP amplitude and latency significantly improved after orbital decompression. Fat and orbital wall decompression are of paramount importance not only to improve exophthalmos and diplopia in patients affected by EO but also as rescue surgery for severe cases where optic neuropathy caused by stretching of the optical nerve is detected by VEP. Imaging and functional nerve evaluation are mandatory in all cases of EO. Copyright © 2012 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

An objective method for measuring face detection thresholds using the sweep steady-state visual evoked response

PubMed Central

Ales, Justin M.; Farzin, Faraz; Rossion, Bruno; Norcia, Anthony M.

2012-01-01

We introduce a sensitive method for measuring face detection thresholds rapidly, objectively, and independently of low-level visual cues. The method is based on the swept parameter steady-state visual evoked potential (ssVEP), in which a stimulus is presented at a specific temporal frequency while parametrically varying (“sweeping”) the detectability of the stimulus. Here, the visibility of a face image was increased by progressive derandomization of the phase spectra of the image in a series of equally spaced steps. Alternations between face and fully randomized images at a constant rate (3/s) elicit a robust first harmonic response at 3 Hz specific to the structure of the face. High-density EEG was recorded from 10 human adult participants, who were asked to respond with a button-press as soon as they detected a face. The majority of participants produced an evoked response at the first harmonic (3 Hz) that emerged abruptly between 30% and 35% phase-coherence of the face, which was most prominent on right occipito-temporal sites. Thresholds for face detection were estimated reliably in single participants from 15 trials, or on each of the 15 individual face trials. The ssVEP-derived thresholds correlated with the concurrently measured perceptual face detection thresholds. This first application of the sweep VEP approach to high-level vision provides a sensitive and objective method that could be used to measure and compare visual perception thresholds for various object shapes and levels of categorization in different human populations, including infants and individuals with developmental delay. PMID:23024355

Involvement of the VEP1 gene in vascular strand development in Arabidopsis thaliana.

PubMed

Jun, Ji Hyung; Ha, Chan Man; Nam, Hong Gil

2002-03-01

A dominant mutant line characterized by abnormal leaf venation pattern was isolated from a transgenic Arabidopsis plant pool that was generated with Agrobacterium culture harboring an Arabidopsis antisense cDNA library. In the mutant line, the phenotype was due to antisense suppression of a gene we named VEP1 (Vein Patterning). The predicted amino acid sequence of the gene contained a motif related to the mammalian death domain that is found in the apoptotic machinery. Reduced expression of the VEP1 gene resulted in the reduced complexity of the venation pattern of the cotyledons and foliar leaves, which was mainly due to the reduced number of the minor veins and their incomplete connection. The analysis of mutant embryos indicated that the phenotype was originated, at least in part, from a defect in the procambium patterning. In the mutant, the stem and root were thinner than those in wild type. This phenotype was associated with reduced vascular development. The promoter activity of the VEP1 gene was detected preferentially in the vascular regions. We propose that the death domain-containing protein VEP1 functions as a positive element required for vascular strand development in Arabidopsis thaliana.

Nonlinear effects in subthreshold virtual electrode polarization.

PubMed

Sambelashvili, Aleksandre T; Nikolski, Vladimir P; Efimov, Igor R

2003-06-01

Introduction of the virtual electrode polarization (VEP) theory suggested solutions to several century-old puzzles of heart electrophysiology including explanation of the mechanisms of stimulation and defibrillation. Bidomain theory predicts that VEPs should exist at any stimulus strength. Although the presence of VEPs for strong suprathreshold pulses has been well documented, their existence at subthreshold strengths during diastole remains controversial. We studied cardiac membrane polarization produced by subthreshold stimuli in 1) rabbit ventricular muscle using high-resolution fluorescent imaging with the voltage-sensitive dye pyridinium 4-[2-[6-(dibutylamino)-2-naphthalenyl]-ethenyl]-1-(3-sulfopropyl)hydroxide (di-4-ANEPPS) and 2) an active bidomain model with Luo-Rudy ion channel kinetics. Both in vitro and in numero models show that the common dog-bone-shaped VEP is present at any stimulus strength during both systole and diastole. Diastolic subthreshold VEPs exhibited nonlinear properties that were expressed in time-dependent asymmetric reversal of membrane polarization with respect to stimulus polarity. The bidomain model reveals that this asymmetry is due to nonlinear properties of the inward rectifier potassium current. Our results suggest that active ion channel kinetics modulate the transmembrane polarization pattern that is predicted by the linear bidomain model of cardiac syncytium.

Retinal nerve fibre thickness measured with optical coherence tomography accurately detects confirmed glaucomatous damage.

PubMed

Hood, D C; Harizman, N; Kanadani, F N; Grippo, T M; Baharestani, S; Greenstein, V C; Liebmann, J M; Ritch, R

2007-07-01

To assess the accuracy of optical coherence tomography (OCT) in detecting damage to a hemifield, patients with hemifield defects confirmed on both static automated perimetry (SAP) and multifocal visual evoked potentials (mfVEP) were studied. Eyes of 40 patients with concomitant SAP and mfVEP glaucomatous loss and 25 controls underwent OCT retinal nerve fibre layer (RNFL), mfVEP and 24-2 SAP tests. For the mfVEP and 24-2 SAP, a hemifield was defined as abnormal based upon cluster criteria. On OCT, a hemifield was considered abnormal if one of the five clock hour sectors (3 and 9 o'clock excluded) was at <1% (red) or two were at <5% (yellow). Seventy seven (43%) of the hemifields were abnormal on both mfVEP and SAP tests. The OCT was abnormal for 73 (95%) of these. Only 1 (1%) of the 100 hemifields of the controls was abnormal on OCT. Sensitivity/specificity (one eye per person) was 95/98%. The OCT RNFL test accurately detects abnormal hemifields confirmed on both subjective and objective functional tests. Identifying abnormal hemifields with a criterion of 1 red (1%) or 2 yellow (5%) clock hours may prove useful in clinical practice.

Prediction of visual evoked potentials at any surface location from a set of three recording electrodes.

PubMed

Mazinani, Babac A E; Waberski, Till D; van Ooyen, Andre; Walter, Peter

2008-05-01

Purpose of this study was to introduce a mathematical model which allows the calculation of a source dipole as the origin of the evoked activity based on the data of three simultaneously recorded VEPs from different locations at the scalp surface to predict field potentials at any neighboring location and to validate this model by comparison with actual recordings. In 10 healthy subjects (25-38, mean 29 years) continuous VEPs were recorded via 96 channels. On the base of the recordings at the positions POz', O1' and O2', a source dipole vector was calculated for each time point of the recordings and VEP responses were back projected for any of the 96 electrode positions. Differences between the calculated and the actually recorded responses were quantified by coefficients of variation (CV). The prediction precision and response size depended on the distance between the electrode of the predicted response and the recording electrodes. After compensating this relationship using a polynomial function, the CV of the mean difference between calculated and recorded responses of the 10 subjects was 2.8 +/- 1.2%. In conclusion, the "Mini-Brainmapping" model can provide precise topographical information with minimal additional recording efforts with good reliability. The implementation of this method in a routine diagnostic setting as an "easy-to-do" procedure would allow to examine a large number of patients and normal subjects in a short time, and thus, a solid data base could be created to correlate well defined pathologies with topographical VEP changes.

Theoretical orientation and therapists' attitudes to important components of therapy: a study based on the valuable elements in psychotherapy questionnaire.

PubMed

Larsson, Billy P M; Kaldo, Viktor; Broberg, Anders G

2010-01-01

The authors describe the inception and subsequent testing of a questionnaire on attitudes regarding how psychotherapy ought to be pursued: the Valuable Elements in Psychotherapy Questionnaire (VEP-Q). A sample of 416 Swedish therapists (161 psychodynamic, 93 cognitive, 95 cognitive behavioral, and 67 integrative/eclectic) responded to the 17-item VEP-Q. A factor analysis of these items resulted in three subscales: PDT, CBT, and Common Factor, as validated by analyses of covariance. The internal consistency and test-retest reliability of the scales were excellent. In addition to theoretical orientation, variables such as gender and basic professional training influenced how respondents answered the VEP-Q. The authors conclude that the VEP-Q seems to be an appropriate instrument for describing similarities as well as differences among practitioners of various schools of psychotherapy.

VEP contrast sensitivity responses reveal reduced functional segregation of mid and high filters of visual channels in autism.

PubMed

Jemel, Boutheina; Mimeault, Daniel; Saint-Amour, Dave; Hosein, Anthony; Mottron, Laurent

2010-06-01

Despite the vast amount of behavioral data showing a pronounced tendency in individuals with autism spectrum disorder (ASD) to process fine visual details, much less is known about the neurophysiological characteristics of spatial vision in ASD. Here, we address this issue by assessing the contrast sensitivity response properties of the early visual-evoked potentials (VEPs) to sine-wave gratings of low, medium and high spatial frequencies in adults with ASD and in an age- and IQ-matched control group. Our results show that while VEP contrast responses to low and high spatial frequency gratings did not differ between ASD and controls, early VEPs to mid spatial frequency gratings exhibited similar response characteristics as those to high spatial frequency gratings in ASD. Our findings show evidence for an altered functional segregation of early visual channels, especially those responsible for processing mid- and high-frequency spatial scales.

Electrophysiological correlates of purely temporal figure-ground segregation.

PubMed

Kandil, Farid I; Fahle, Manfred

2003-11-01

Inhomogenous displays, in contrast to homogenous ones, evoke a specific potential in the VEP (tsVEP) which appears across different classical visual stimulus dimensions defining figure-ground segregation, such as luminance, orientation, (first-order) motion, and stereoscopic depth. This negative potential has a peak latency of about 200-300 ms and a peak amplitude of about -3 to -10 microV [Doc Ophthalmol. 95 (1998) 335]. Previously, we demonstrated that human subjects reliably segregate figure from ground, even in the absence of the classical cues, leaving time of change as the only cue for segregation. The results of the present study demonstrate that also purely temporally defined checkerboards evoke a tsVEP resembling the motion-defined tsVEP regarding polarity (negative), latency (two peaks at 180 and 270 ms, respectively), amplitude of the first negativity (-5.6 microV), and overall form of its components.

Visual evoked potentials through night vision goggles.

PubMed

Rabin, J

1994-04-01

Night vision goggles (NVG's) have widespread use in military and civilian environments. NVG's amplify ambient illumination making performance possible when there is insufficient illumination for normal vision. While visual performance through NVG's is commonly assessed by measuring threshold functions such as visual acuity, few attempts have been made to assess vision through NVG's at suprathreshold levels of stimulation. Such information would be useful to better understand vision through NVG's across a range of stimulus conditions. In this study visual evoked potentials (VEP's) were used to evaluate vision through NVG's across a range of stimulus contrasts. The amplitude and latency of the VEP varied linearly with log contrast. A comparison of VEP's recorded with and without NVG's was used to estimate contrast attenuation through the device. VEP's offer an objective, electrophysiological tool to assess visual performance through NVG's at both threshold and suprathreshold levels of visual stimulation.

Effect of mechanical tactile noise on amplitude of visual evoked potentials: multisensory stochastic resonance.

PubMed

Méndez-Balbuena, Ignacio; Huidobro, Nayeli; Silva, Mayte; Flores, Amira; Trenado, Carlos; Quintanar, Luis; Arias-Carrión, Oscar; Kristeva, Rumyana; Manjarrez, Elias

2015-10-01

The present investigation documents the electrophysiological occurrence of multisensory stochastic resonance in the human visual pathway elicited by tactile noise. We define multisensory stochastic resonance of brain evoked potentials as the phenomenon in which an intermediate level of input noise of one sensory modality enhances the brain evoked response of another sensory modality. Here we examined this phenomenon in visual evoked potentials (VEPs) modulated by the addition of tactile noise. Specifically, we examined whether a particular level of mechanical Gaussian noise applied to the index finger can improve the amplitude of the VEP. We compared the amplitude of the positive P100 VEP component between zero noise (ZN), optimal noise (ON), and high mechanical noise (HN). The data disclosed an inverted U-like graph for all the subjects, thus demonstrating the occurrence of a multisensory stochastic resonance in the P100 VEP. Copyright © 2015 the American Physiological Society.

Distinct Visual Evoked Potential Morphological Patterns for Apparent Motion Processing in School-Aged Children.

PubMed

Campbell, Julia; Sharma, Anu

2016-01-01

Measures of visual cortical development in children demonstrate high variability and inconsistency throughout the literature. This is partly due to the specificity of the visual system in processing certain features. It may then be advantageous to activate multiple cortical pathways in order to observe maturation of coinciding networks. Visual stimuli eliciting the percept of apparent motion and shape change is designed to simultaneously activate both dorsal and ventral visual streams. However, research has shown that such stimuli also elicit variable visual evoked potential (VEP) morphology in children. The aim of this study was to describe developmental changes in VEPs, including morphological patterns, and underlying visual cortical generators, elicited by apparent motion and shape change in school-aged children. Forty-one typically developing children underwent high-density EEG recordings in response to a continuously morphing, radially modulated, circle-star grating. VEPs were then compared across the age groups of 5-7, 8-10, and 11-15 years according to latency and amplitude. Current density reconstructions (CDR) were performed on VEP data in order to observe activated cortical regions. It was found that two distinct VEP morphological patterns occurred in each age group. However, there were no major developmental differences between the age groups according to each pattern. CDR further demonstrated consistent visual generators across age and pattern. These results describe two novel VEP morphological patterns in typically developing children, but with similar underlying cortical sources. The importance of these morphological patterns is discussed in terms of future studies and the investigation of a relationship to visual cognitive performance.

Basophil mediated pro-allergic inflammation in vehicle-emitted particles exposure.

PubMed

Zakharenko, Alexander M; Engin, Ayse Basak; Chernyshev, Valery V; Chaika, Vladimir V; Ugay, Sergey M; Rezaee, Ramin; Karimi, Gholamreza; Drozd, Vladimir A; Nikitina, Anna V; Solomennik, Sergey F; Kudryavkina, Olga R; Xin, Liu; Wenpeng, Yuan; Tzatzarakis, Manolis; Tsatsakis, Aristidis M; Golokhvast, Kirill S

2017-01-01

Despite of the fact that engine manufacturers develop a new technology to reduce exhaust emissions, insufficient attention given to particulate emissions. However, diesel exhaust particles are a major source of air-borne pollution, contain vast amount of polycyclic aromatic hydrocarbons (PAHs) and may have deleterious effects on the immune system, resulting in the induction and enhancement of pro-allergic processes. In the current study, vehicle emitted particles (VEP) from 2 different types of cars (diesel - D and gasoline - G) and locomotive (L) were collected. Overall, 129 four-week-old, male SPF-class Kunming mice were subcutaneously instilled with either low dose 100, 250 or high dose, 500mg/kg VEP and 15 mice were assigned as control group. The systemic toxicity was evaluated and alterations in the percentages of the CD3, CD4, CD8, CD16, CD25 expressing cells, basophils, eosinophils and neutrophils were determined. Basophil percentages were inversely associated with the PAH content of the VEPs, however basophil sensitization was more important than cell count in VEP exposure. Thus, the effects of VEP-PAHs emerge with the activation of basophils in an allergen independent fashion. Despite the increased percentage of CD4+ T cells, a sharp decrease in basophil counts at 500mg/kg of VEP indicates a decreased inhibitory effect of CD16+ monocytes on the proliferation of CD4+ T cell and suppressed polarization into a Th2 phenotype. Therefore, although the restrictions for vehicles emissions differ between countries, follow up studies and strict regulations are needed. Copyright © 2016 Elsevier Inc. All rights reserved.

Brief monocular deprivation as an assay of short-term visual sensory plasticity in schizophrenia - "the binocular effect".

PubMed

Foxe, John J; Yeap, Sherlyn; Leavitt, Victoria M

2013-01-01

Visual sensory processing deficits are consistently observed in schizophrenia, with clear amplitude reduction of the visual evoked potential (VEP) during the initial 50-150 ms of processing. Similar deficits are seen in unaffected first-degree relatives and drug-naïve first-episode patients, pointing to these deficits as potential endophenotypic markers. Schizophrenia is also associated with deficits in neural plasticity, implicating dysfunction of both glutamatergic and GABAergic systems. Here, we sought to understand the intersection of these two domains, asking whether short-term plasticity during early visual processing is specifically affected in schizophrenia. Brief periods of monocular deprivation (MD) induce relatively rapid changes in the amplitude of the early VEP - i.e., short-term plasticity. Twenty patients and 20 non-psychiatric controls participated. VEPs were recorded during binocular viewing, and were compared to the sum of VEP responses during brief monocular viewing periods (i.e., Left-eye + Right-eye viewing). Under monocular conditions, neurotypical controls exhibited an effect that patients failed to demonstrate. That is, the amplitude of the summed monocular VEPs was robustly greater than the amplitude elicited binocularly during the initial sensory processing period. In patients, this "binocular effect" was absent. Patients were all medicated. Ideally, this study would also include first-episode unmedicated patients. These results suggest that short-term compensatory mechanisms that allow healthy individuals to generate robust VEPs in the context of MD are not effectively activated in patients with schizophrenia. This simple assay may provide a useful biomarker of short-term plasticity in the psychotic disorders and a target endophenotype for therapeutic interventions.

Distinct Visual Evoked Potential Morphological Patterns for Apparent Motion Processing in School-Aged Children

PubMed Central

Campbell, Julia; Sharma, Anu

2016-01-01

Measures of visual cortical development in children demonstrate high variability and inconsistency throughout the literature. This is partly due to the specificity of the visual system in processing certain features. It may then be advantageous to activate multiple cortical pathways in order to observe maturation of coinciding networks. Visual stimuli eliciting the percept of apparent motion and shape change is designed to simultaneously activate both dorsal and ventral visual streams. However, research has shown that such stimuli also elicit variable visual evoked potential (VEP) morphology in children. The aim of this study was to describe developmental changes in VEPs, including morphological patterns, and underlying visual cortical generators, elicited by apparent motion and shape change in school-aged children. Forty-one typically developing children underwent high-density EEG recordings in response to a continuously morphing, radially modulated, circle-star grating. VEPs were then compared across the age groups of 5–7, 8–10, and 11–15 years according to latency and amplitude. Current density reconstructions (CDR) were performed on VEP data in order to observe activated cortical regions. It was found that two distinct VEP morphological patterns occurred in each age group. However, there were no major developmental differences between the age groups according to each pattern. CDR further demonstrated consistent visual generators across age and pattern. These results describe two novel VEP morphological patterns in typically developing children, but with similar underlying cortical sources. The importance of these morphological patterns is discussed in terms of future studies and the investigation of a relationship to visual cognitive performance. PMID:27445738

Our initial experience with ventriculo-epiplooic shunt in treatment of hydrocephalus in two centers.

PubMed

Grigorean, Valentin Titus; Sandu, Aurelia Mihaela; Popescu, Mihai; Florian, Ioan Stefan; Lupascu, Cristian Dumitru; Ursulescu, Corina Lupascu

Hydrocephalus represents impairment in cerebrospinal fluid (CSF) dynamics. If the treatment of hydrocephalus is considered difficult, the repeated revisions of ventriculo-peritoneal (VP) shunts are even more challenging. The aim of this article is to evaluate the efficiency of ventriculo-epiplooic (VEp) shunt as a feasible alternative in hydrocephalic patients. A technical modification regarding the insertion of peritoneal catheter was imagined: midline laparotomy 8-10cm long was performed in order to open the peritoneal cavity; the great omentum was dissected between its two layers; we placed the distal end of the catheter between the two epiplooic layers; a fenestration of 4cm in diameter into the visceral layer was also performed. A retrospective study of medical records of 15 consecutive patients with hydrocephalus treated with VEp shunt is also presented. Between 2008 and 2014 we performed VEp shunt in 15 patients: 5 with congenital hydrocephalus, 8 with secondary hydrocephalus and 2 with normal pressure hydrocephalus. There were 7 men and 8 women. VEp shunt was performed in 13 patients with multiple distal shunt failures and in 2 patients, with history of abdominal surgery, as de novo extracranial drainage procedure. The outcome was favorable in all cases, with no significant postoperative complications. VEp shunt is a new, safe and efficient surgical technique for the treatment of hydrocephalus. VEp shunt is indicated in patients with history of recurrent distal shunt failures, and in patients with history of open abdominal surgery and high risk for developing abdominal complications. Copyright © 2017 Polish Neurological Society. Published by Elsevier Urban & Partner Sp. z o.o. All rights reserved.

Skier and Snowboarder Motivations and Knowledge Related to Voluntary Environmental Programs at an Alpine Ski Area

NASA Astrophysics Data System (ADS)

Little, Christopher M.; Needham, Mark D.

2011-11-01

Many alpine ski areas have recently adopted voluntary environmental programs (VEPs) such as using recycling, renewable energy, and biofuels to help reduce their environmental impacts. Studies have addressed the performance of these VEPs in mitigating environmental impacts of this industry, but little is known about visitor awareness and perceptions of these programs. This article addresses this knowledge gap by exploring skier and snowboarder knowledge of VEPs at a ski area and the influence of these programs on their motivations to visit this area currently and behavioral intentions to visit again in the future. Data were obtained from an onsite survey at the Mt. Bachelor ski area in Oregon, USA ( n = 429, 89.7% response rate). Few skiers and snowboarders were knowledgeable of VEPs at this area and fewer than 20% were motivated to visit on their current trip because of these programs. Other attributes such as scenery, snow conditions, and access were more important for influencing visitation. Up to 38% of skiers and snowboarders, however, intend to visit this ski area more often if it adopts and promotes more VEPs. Managers can use these results to inform communication and marketing of their environmental programs and performance to visitors. Additional implications for management and future research are discussed.

Skier and snowboarder motivations and knowledge related to voluntary environmental programs at an alpine ski area.

PubMed

Little, Christopher M; Needham, Mark D

2011-11-01

Many alpine ski areas have recently adopted voluntary environmental programs (VEPs) such as using recycling, renewable energy, and biofuels to help reduce their environmental impacts. Studies have addressed the performance of these VEPs in mitigating environmental impacts of this industry, but little is known about visitor awareness and perceptions of these programs. This article addresses this knowledge gap by exploring skier and snowboarder knowledge of VEPs at a ski area and the influence of these programs on their motivations to visit this area currently and behavioral intentions to visit again in the future. Data were obtained from an onsite survey at the Mt. Bachelor ski area in Oregon, USA (n = 429, 89.7% response rate). Few skiers and snowboarders were knowledgeable of VEPs at this area and fewer than 20% were motivated to visit on their current trip because of these programs. Other attributes such as scenery, snow conditions, and access were more important for influencing visitation. Up to 38% of skiers and snowboarders, however, intend to visit this ski area more often if it adopts and promotes more VEPs. Managers can use these results to inform communication and marketing of their environmental programs and performance to visitors. Additional implications for management and future research are discussed.

Influence of rotating shift work on visual reaction time and visual evoked potential.

PubMed

R V, Hemamalini; N, Krishnamurthy; A, Saravanan

2014-10-01

The present day life style is changing the circadian rhythm of the body especially in rotating night shift workers. The impact of this prolongs their reaction time. Night shift also interferes with the circadian variation of pupil size which may affect the visual evoked potential. To compare the visual reaction time, visual evoked potential (VEP) in rotating night shift workers & day workers and also to correlate the changes in visual reaction time with visual evoked potential. Forty healthy male security guards & staff (25 - 35 y) who did rotating night shifts at least for six months & 40 d workers (25 - 35 y) who did not do night shift in last two years were involved in the study. Visual reaction time and the latency & amplitude of VEP were recorded. Kolmogorov- Smirnov test for normalcy showed the latencies & amplitude of VEP to be normally distributed. Student's unpaired t test showed significant difference (p<0.05) in the visual time and in the latencies of VEP between night shift & day workers. There was no significant difference in the amplitude of VEP. Night shift workers who are prone to circadian rhythm alteration will have prolonged visual reaction time & visual evoked potential abnormalities. Implementation of Bright Light Therapy would be beneficial to the night shift worker.

Visual and brainstem auditory evoked potentials in infants with severe vitamin B12 deficiency.

PubMed

Demir, Nihat; Koç, Ahmet; Abuhandan, Mahmut; Calik, Mustafa; Işcan, Akin

2015-01-01

Vitamin B12 plays an important role in the development of mental, motor, cognitive, and social functions via its role in DNA synthesis and nerve myelination. Its deficiency in infants might cause neuromotor retardation as well as megaloblastic anemia. The objective of this study was to investigate the effects of infantile vitamin B12 deficiency on evoked brain potentials and determine whether improvement could be obtained with vitamin B12 replacement at appropriate dosages. Thirty patients with vitamin B12 deficiency and 30 age-matched healthy controls were included in the study. Hematological parameters, visual evoked potentials, and brainstem auditory evoked potentials tests were performed prior to treatment, 1 week after treatment, and 3 months after treatment. Visual evoked potentials (VEPs) and brainstem auditory evoked potentials (BAEPs) were found to be prolonged in 16 (53.3%) and 15 (50%) patients, respectively. Statistically significant improvements in VEP and BAEP examinations were determined 3 months after treatment. Three months after treatment, VEP and BAEP examinations returned to normal in 81.3% and 53.3% of subjects with prolonged VEPs and BAEPs, respectively. These results demonstrate that vitamin B12 deficiency in infants causes significant impairment in the auditory and visual functioning tests of the brain, such as VEP and BAEP.

Relationship between vitamin D deficiency and visually evoked potentials in multiple sclerosis.

PubMed

López-Méndez, P; Sosa-Henríquez, M; Ruiz-Pérez, Á

2016-05-01

To evaluate the possible relationship between serum 25-OH vitamin D levels and visually evoked potentials (VEP) in patients with multiple sclerosis (MS), residents in the south zone of Gran Canaria. The study included 49 patients with MS, on whom 25-OH-vitamin D was determined, along with VEP, and a neurological examination to determine incapacity. Clinical variables, such as a history of optic neuritis were recorded. The mean value of 25-OH-vitamin D of the patients was 28.1±9.5ng/ml. The VEP latency was 119.1±23.2ms and the amplitude, 8.5±4.4 μV. Patients with a higher 25-OH-vitamin D had a greater number of outbreaks in the year prior to the study (P=.049), and those with vitamin D deficiency and previous optic neuritis showed no reduction in the amplitude of the VEP (P=.006). Patients with vitamin D deficiency have lower clinical activity of the MS and show no axonal involvement in VEP after having suffered optic neuritis. These relationships, although statistically significant, do not seem clinically plausible, thus new studies are needed to try and confirm this possible relationship. Copyright © 2016 Sociedad Española de Oftalmología. Published by Elsevier España, S.L.U. All rights reserved.

SU5. Investigation of the Visual Steady-State Response in Schizophrenia, Schizoaffective, Psychotic, and Nonpsychotic Bipolar Disorders

PubMed Central

Schneider, Zoe; Parker, David; Kittle, Frances; McDowell, Jennifer; Buckley, Peter; Keedy, Sarah; Gershon, Elliot; Sweeney, John; Keshavan, Matcheri; Pearlson, Godfrey; Tamminga, Carol; Clementz, Brett

2017-01-01

Abstract Background: Electroencephalographic (EEG) studies of the visual steady-state response (ssVEP) probe the oscillatory capacity and synchronization in the primary visual cortex. Previous ssVEP studies have demonstrated early visual processing deficits in schizophrenia (SZ). However, few studies have examined the ssVEP across diagnostic categories and included the full spectrum of psychotic subgroups (schizophrenia: SZ, schizoaffective disorder: SAD, bipolar disorder with psychosis: BDP, and bipolar disorder without psychosis: BD-NP). This is a critical step in order to investigate its potential as a biomarker and to examine specific neural deficits that are unique to each disorder. In this study visual steady-state stimuli in the central, bilateral, left, and right hemisphere were administered to a large sample of well characterized participants diagnosed with SZ, SAD, BDP, or BD-NP. Methods: Four hundred and seven individuals (HC = 153, SZ = 64, SAD = 79, BDP = 65, BD-NP = 46) completed the ssVEP EEG task at the 5 BSNIP sites. A black and white square oscillating at 18.75 Hz was placed in the subject’s central, bilateral, left, and right visual field for 2000 ms. Inter-trial phase coherence (ITC) was calculated for each subject, sensor, and task. The resulting time-frequency values ranged from 4 to 53 Hz and −500 to 2000 ms poststimulus. The 7 peak sensors from the grand average for each task were selected and used to average over the 0–2000 ms ssVEP period for each subject. One-way ANOVA’s and Welch’s t tests were conducted to determine group differences for each task. Results: SAD had significantly reduced ITC in comparison to HC during the bilateral ssVEP task. SZ and SAD both had significantly reduced ITC in comparison to HC and BD-NP during the center visual field trials. There were no significant group differences in either left or right visual field trials for any of the groups. BDP and BD-NP did not differ from HC in any of the conditions. Conclusion: There are 2 main conclusions that can be drawn from this study. (1) Both SZ and SAD had a reduced response to the central stimuli. This is suggestive of a core deficit at the beginning of the visual processing pathway. (2) SAD had a reduction in response the bilateral stimuli. This suggests that SAD has a unique deficit in interhemispheric visual response that is not found in any of the other psychotic or bipolar disorders. Examining differences in the ssVEP between proband groups offers unique insight into how neural synchronization relates to the etiology of SZ and SAD. This provides novel information about core visual processing deficits that could potentially be used as a translational biomarker.

Deep brain stimulation of the subthalamic nucleus affects resting EEG and visual evoked potentials in Parkinson's disease.

PubMed

Jech, Robert; Růzicka, Evzen; Urgosík, Dusan; Serranová, Tereza; Volfová, Markéta; Nováková, Olga; Roth, Jan; Dusek, Petr; Mecír, Petr

2006-05-01

We studied changes of the EEG spectral power induced by deep brain stimulation (DBS) of the subthalamic nucleus (STN) in patients with Parkinson's disease (PD). Also analyzed were changes of visual evoked potentials (VEP) with DBS on and off. Eleven patients with advanced PD treated with bilateral DBS STN were examined after an overnight withdrawal of L-DOPA and 2 h after switching off the neurostimulators. All underwent clinical examination followed by resting EEG and VEP recordings, a procedure repeated after DBS STN was switched on. With DBS switched on, the dominant EEG frequency increased from 9.44+/-1.3 to 9.71+/-1.3 Hz (P<0.01) while its relative spectral power dropped by 11% on average (P<0.05). Switching on the neurostimulators caused a decrease in the N70/P100 amplitude of the VEP (P<0.01), which inversely correlated with the intensity of DBS (black-and-white pattern: P<0.01; color pattern: P<0.05). Despite artifacts generated by neurostimulators, the VEP and resting EEG were suitable for the detection of effects related to DBS STN. The acceleration of dominant frequency in the alpha band may be evidence of DBS STN influence on speeding up of intracortical oscillations. The spectral power decrease, seen mainly in the fronto-central region, might reflect a desynchronization in the premotor and motor circuits, though no movement was executed. Similarly, desynchronization of the cortical activity recorded posteriorly may by responsible for the VEP amplitude decrease implying DBS STN-related influence even on the visual system. Changes in idling EEG activity observed diffusely over scalp together with involvement of the VEP suggest that the effects of DBS STN reach far beyond the motor system influencing the basic mechanisms of rhythmic cortical oscillations.

Role of inter-hemispheric transfer in generating visual evoked potentials in V1-damaged brain hemispheres

PubMed Central

Kavcic, Voyko; Triplett, Regina L.; Das, Anasuya; Martin, Tim; Huxlin, Krystel R.

2015-01-01

Partial cortical blindness is a visual deficit caused by unilateral damage to the primary visual cortex, a condition previously considered beyond hopes of rehabilitation. However, recent data demonstrate that patients may recover both simple and global motion discrimination following intensive training in their blind field. The present experiments characterized motion-induced neural activity of cortically blind (CB) subjects prior to the onset of visual rehabilitation. This was done to provide information about visual processing capabilities available to mediate training-induced visual improvements. Visual Evoked Potentials (VEPs) were recorded from two experimental groups consisting of 9 CB subjects and 9 age-matched, visually-intact controls. VEPs were collected following lateralized stimulus presentation to each of the 4 visual field quadrants. VEP waveforms were examined for both stimulus-onset (SO) and motion-onset (MO) related components in postero-lateral electrodes. While stimulus presentation to intact regions of the visual field elicited normal SO-P1, SO-N1, SO-P2 and MO-N2 amplitudes and latencies in contralateral brain regions of CB subjects, these components were not observed contralateral to stimulus presentation in blind quadrants of the visual field. In damaged brain hemispheres, SO-VEPs were only recorded following stimulus presentation to intact visual field quadrants, via inter-hemispheric transfer. MO-VEPs were only recorded from damaged left brain hemispheres, possibly reflecting a native left/right asymmetry in inter-hemispheric connections. The present findings suggest that damaged brain hemispheres contain areas capable of responding to visual stimulation. However, in the absence of training or rehabilitation, these areas only generate detectable VEPs in response to stimulation of the intact hemifield of vision. PMID:25575450

Cost-effectiveness of a vocational enablement protocol for employees with hearing impairment; design of a randomized controlled trial

PubMed Central

2012-01-01

Background Hearing impairment at the workplace, and the resulting psychosocial problems are a major health problem with substantial costs for employees, companies, and society. Therefore, it is important to develop interventions to support hearing impaired employees. The objective of this article is to describe the design of a randomized controlled trial evaluating the (cost-) effectiveness of a Vocational Enablement Protocol (VEP) compared with usual care. Methods/Design Participants will be selected with the 'Hearing and Distress Screener'. The study population will consist of 160 hearing impaired employees. The VEP intervention group will be compared with usual care. The VEP integrated care programme consists of a multidisciplinary assessment of auditory function, work demands, and personal characteristics. The goal of the intervention is to facilitate participation in work. The primary outcome measure of the study is 'need for recovery after work'. Secondary outcome measures are coping with hearing impairment, distress, self-efficacy, psychosocial workload, job control, general health status, sick leave, work productivity, and health care use. Outcome measures will be assessed by questionnaires at baseline, and 3, 6, 9, and 12 months after baseline. The economic evaluation will be performed from both a societal and a company perspective. A process evaluation will also be performed. Discussion Interventions addressing occupational difficulties of hearing impaired employees are rare but highly needed. If the VEP integrated care programme proves to be (cost-) effective, the intervention can have an impact on the well-being of hearing impaired employees, and thereby, on the costs for the company as well for the society. Trial registration Netherlands Trial Register (NTR): NTR2782 PMID:22380920

Visual evoked potential assessment of the effects of glaucoma on visual subsystems.

PubMed

Greenstein, V C; Seliger, S; Zemon, V; Ritch, R

1998-06-01

The purpose of this study is to test the hypothesis that glaucoma leads to selective deficits in parallel pathways or channels. Sweep VEPs were obtained to isolated-check stimuli that were modulated sinusoidally in either isoluminant chromatic contrast or in positive and negative luminance contrast. Response functions were obtained from 14 control subjects, 15 patients with open-angle glaucoma, and seven glaucoma suspects. For all three groups of subjects we found characteristic differences between the VEP response functions to isoluminant chromatic contrast stimuli and to luminance contrast stimuli. The isoluminant chromatic stimulus conditions appeared to favor activity of the P-pathway, whereas the luminance contrast stimuli at low depths of modulation favored M-pathway activity. VEP responses for patients with OAG were significantly reduced for chromatic contrast and luminance contrast conditions, whereas VEP responses for glaucoma suspects were significantly reduced only for the 15-Hz positive luminance contrast condition. Our results suggest that both M- and P-pathways are affected by glaucoma.

Effect of oculomotor vision rehabilitation on the visual-evoked potential and visual attention in mild traumatic brain injury.

PubMed

Yadav, Naveen K; Thiagarajan, Preethi; Ciuffreda, Kenneth J

2014-01-01

The purpose of the experiment was to investigate the effect of oculomotor vision rehabilitation (OVR) on the visual-evoked potential (VEP) and visual attention in the mTBI population. Subjects (n = 7) were adults with a history of mild traumatic brain injury (mTBI). Each received 9 hours of OVR over a 6-week period. The effects of OVR on VEP amplitude and latency, the attention-related alpha band (8-13 Hz) power (µV(2)) and the clinical Visual Search and Attention Test (VSAT) were assessed before and after the OVR. After the OVR, the VEP amplitude increased and its variability decreased. There was no change in VEP latency, which was normal. Alpha band power increased, as did the VSAT score, following the OVR. The significant changes in most test parameters suggest that OVR affects the visual system at early visuo-cortical levels, as well as other pathways which are involved in visual attention.

Effect of ethanol on the visual-evoked potential in rat: dynamics of ON and OFF responses.

PubMed

Dulinskas, Redas; Buisas, Rokas; Vengeliene, Valentina; Ruksenas, Osvaldas

2017-01-01

The effect of acute ethanol administration on the flash visual-evoked potential (VEP) was investigated in numerous studies. However, it is still unclear which brain structures are responsible for the differences observed in stimulus onset (ON) and offset (OFF) responses and how these responses are modulated by ethanol. The aim of our study was to investigate the pattern of ON and OFF responses in the visual system, measured as amplitude and latency of each VEP component following acute administration of ethanol. VEPs were recorded at the onset and offset of a 500 ms visual stimulus in anesthetized male Wistar rats. The effect of alcohol on VEP latency and amplitude was measured for one hour after injection of 2 g/kg ethanol dose. Three VEP components - N63, P89 and N143 - were analyzed. Our results showed that, except for component N143, ethanol increased the latency of both ON and OFF responses in a similar manner. The latency of N143 during OFF response was not affected by ethanol but its amplitude was reduced. Our study demonstrated that the activation of the visual system during the ON response to a 500 ms visual stimulus is qualitatively different from that during the OFF response. Ethanol interfered with processing of the stimulus duration at the level of the visual cortex and reduced the activation of cortical regions.

Spillover Effects of Voluntary Environmental Programs on Greenhouse Gas Emissions: Lessons from Mexico

ERIC Educational Resources Information Center

Henriques, Irene; Husted, Bryan W.; Montiel, Ivan

2013-01-01

We compare the environmental performance of voluntary environmental programs (VEPs) with different attributes. Using club theory, we argue that the differential performance of VEPs is due in part to their specific design attributes that will either enhance or diminish their ability to improve both targeted and untargeted environmental impacts. We…

Effects of nicergoline on the retinal and cortical electrophysiological responses in glaucoma patients: a preliminary open study.

PubMed

Parisi, V; Colacino, G; Milazzo, G; Scuderi, A C; Manni, G

1999-09-01

The retinal dysfunction and the delayed visual cortex responses shown by patients affected by glaucoma can be objectively assessed by Pattern Electroretinogram (PERG) and Visual Evoked Potentials (VEP) recordings. The present study aims to evaluate the effects of nicergoline on the retinal function and on the visual cortical responses in glaucoma patients. Sixty patients (mean age 44.6+/-3.7) with open angle glaucoma were enrolled. The patients were divided into two groups: NG Group, where 30 patients were treated with nicergoline (Cebran((R)), 2 cps day) for 30 days; and CG Group, where 30 patients were not treated. Simultaneous recordings of PERG and VEP were performed in NG patients at the baseline, at 30 days after treatment with nicergoline (day 30), and at 45 days from the end of the treatment (day 75). PERG and VEP were recorded in CG patients at the baseline and after 30 and 75 days. The visual stimulus for recording PERGs and VEPs was a checkerboard whose elements subtended a visual arc of 60' and 15' with a 70% contrast, and alternated at a frequency of 2 Hz. At the baseline none of the electrophysiological parameters observed in NG Group patients differed (P>0.05) from those of CG Group patients. At days 30 and 75, in CG Group patients the values of the PERG and VEP parameters were unmodified (P>0.05) with respect to the baseline. In NG Group patients, the 30-day treatment period with nicergoline induced a significant (P<0.01) improvement of the PERG and VEP parameters. At day 75 all the electrophysiological parameters of NG Group did not differ significantly (P>0.05) from those at the baseline. Treatment with nicergoline induces an improvement of the retinal function and of the visual cortical responses in patients affected by glaucoma. This effect disappears within 45 days after the suspension of the treatment. Copyright 1999 Academic Press.

Electric field encephalography for brain activity monitoring.

PubMed

Versek, Craig William; Frasca, Tyler; Zhou, Jianlin; Chowdhury, Kaushik; Sridhar, Srinivas

2018-05-11

Objective - We describe an early-stage prototype of a new wireless electrophysiological sensor system, called NeuroDot, which can measure neuroelectric potentials and fields at the scalp in a new modality called Electric Field Encephalography (EFEG). We aim to establish the physical validity of the EFEG modality, and examine some of its properties and relative merits compared to EEG. Approach - We designed a wireless neuroelectric measurement device based on the Texas Instrument ADS1299 Analog Front End platform and a sensor montage, using custom electrodes, to simultaneously measure EFEG and spatially averaged EEG over a localized patch of the scalp (2cm x 2cm). The signal properties of each modality were compared across tests of noise floor, Berger effect, steady-state Visually Evoked Potential (ssVEP), signal-to-noise ratio (SNR), and others. In order to compare EFEG to EEG modalities in the frequency domain, we use a novel technique to compute spectral power densities and derive narrow-band SNR estimates for ssVEP signals. A simple binary choice brain-computer-interface (BCI) concept based on ssVEP is evaluated. Also, we present examples of high quality recording of transient Visually Evoked Potentials and Fields (tVEPF) that could be used for neurological studies. Main results - We demonstrate the capability of the NeuroDot system to record high quality EEG signals comparable to some recent clinical and research grade systems on the market. We show that the locally-referenced EFEG metric is resistant to certain types of movement artifacts. In some ssVEP based measurements, the EFEG modality shows promising results, demonstrating superior signal to noise ratios than the same recording processed as an analogous EEG signal. We show that by using EFEG based ssVEP SNR estimates to perform a binary classification in a model BCI, the optimal information transfer rate (ITR) can be raised from 15 to 30 bits per minute - though these preliminary results are likely sensitive to inter-subject variations and choice of scalp locations, so require further investigation. Significance - Enhancement of ssVEP SNR using EFEG has the potential to improve visually based BCIs and diagnostic paradigms. The time domain analysis of tVEPF signals shows robust features in the electric field components that might have clinical relevance beyond classical VEP approaches. . © 2018 IOP Publishing Ltd.

120-W 2-µm thulium:yttrium-aluminium-garnet vapoenucleation of the prostate: 12-month follow-up.

PubMed

Netsch, Christopher; Pohlmann, Laura; Herrmann, Thomas R W; Gross, Andreas J; Bach, Thorsten

2012-07-01

Study Type - Therapy (case series) Level of Evidence 4 What's known on the subject? and What does the study add? Thulium VapoEnucleation of the prostate (ThuVEP) has been introduced as a minimally invasive treatment modality of benign prostate obstruction (BPO). This study reports the largest series of patients with symptomatic BPO undergoing ThuVEP. Efficacy of this procedure was confirmed by prostate volume and PSA measurements at 12-month follow up, which have not been reported after ThuVEP so far. To evaluate the safety and efficacy of 120-W 2-µm thulium:yttrium-aluminium-garnet (YAG) vapoenucleation of the prostate (ThuVEP) for patients with symptomatic benign prostatic obstruction. In total, 207 consecutive patients undergoing ThuVEP at our institution were evaluated prospectively. ThuVEP was carried out using the 120-W 2-µm continuous-wave Tm:YAG laser. The enucleated tissue was then morcellated within the bladder. Patient demographic, perioperative and 12-month follow-up data were analysed. The complications were assessed. Mean preoperative prostate volume was 57.8 ± 31.5 mL. Total operation duration averaged 64.9 ± 29.9 min, and the enucleation time was 36.5 ± 20.1 min. The mean catheter time was 2.2 ± 0.6 days. Thirteen (6.28%) patients required a second-look operation in the immediate postoperative course (failed morcellation n= 1, clot retention n= 4, residual tissue at the apex of the prostate n= 8). Four patients needed blood transfusions (1.93%) postoperatively. In all, 147 (71%) patients were available for review at the 12-month follow-up mark. Quality of life (4.4 ± 1.3 vs 1.2 ± 1.1), international prostate symptom score (21.9 ± 7.2 vs 5.1 ± 4), maximum urinary flow rate (9.4 ± 3.8 vs 23.5 ± 10.9 mL/s), postvoiding residual urine (159.2 ± 153.2 vs 26.7 ± 38.3 mL), prostate-specific antigen (5.0 ± 5.2 vs 0.6 ± 0.5 ng/mL) and prostate volume (57.8 ± 31.5 vs 10.7 ± 4.4 mL) changed significantly (P= 0.000). Median prostate-specific antigen reduction and prostate volume reduction were 87% and 80% respectively at follow-up. Urethral stricture and bladder neck contracture developed in 1.45% and 1.93% respectively of the patients. 120-W ThuVEP is a safe and efficacious procedure for the treatment of symptomatic benign prostatic obstruction. The incidence of complications with ThuVEP was low. © 2011 BJU INTERNATIONAL.

Adaptive regularization network based neural modeling paradigm for nonlinear adaptive estimation of cerebral evoked potentials.

PubMed

Zhang, Jian-Hua; Böhme, Johann F

2007-11-01

In this paper we report an adaptive regularization network (ARN) approach to realizing fast blind separation of cerebral evoked potentials (EPs) from background electroencephalogram (EEG) activity with no need to make any explicit assumption on the statistical (or deterministic) signal model. The ARNs are proposed to construct nonlinear EEG and EP signal models. A novel adaptive regularization training (ART) algorithm is proposed to improve the generalization performance of the ARN. Two adaptive neural modeling methods based on the ARN are developed and their implementation and performance analysis are also presented. The computer experiments using simulated and measured visual evoked potential (VEP) data have shown that the proposed ARN modeling paradigm yields computationally efficient and more accurate VEP signal estimation owing to its intrinsic model-free and nonlinear processing characteristics.

Restoration of visual response in aged dystrophic RCS rats using AAV-mediated channelopsin-2 gene transfer.

PubMed

Tomita, Hiroshi; Sugano, Eriko; Yawo, Hiromu; Ishizuka, Toru; Isago, Hitomi; Narikawa, Satoko; Kügler, Sebastian; Tamai, Makoto

2007-08-01

To investigate whether the channelopsin-2 (Chop2) gene would restore visual responses in 10-month-old dystrophic Royal College of Surgeons (aged RCS; rdy/rdy) rats, the authors transferred the Chop2 gene into the retinal cells of aged RCS rats using the adenoassociated virus (AAV) vector. The N-terminal fragment (residues 1-315) of Chop2 was fused to a fluorescent protein, Venus, in frame at the end of the Chop2 coding fragment. The viral vector construct (AAV-Chop2V) for the expression of the Chop2V in the retina was made by subcloning into an adenoassociated virus vector, including the CAG promoter. To evaluate the expression profile of Chop2V in the retina, the rats were killed and the eyes were removed and fixed with 4% paraformaldehyde in 0.1 M phosphate-buffered saline. Retinal wholemount specimens and cryosections were made. Under anesthetized conditions, electrodes for the recording of visually evoked potentials (VEPs) were implanted onto the visual cortex in aged-RCS (rdy/rdy) rats. AAV-Chop2V vectors were then injected into the vitreous cavity of the left eyes. As a control, AAV-Venus vectors were applied to the right eyes. VEPs were evoked by the flash of a blue, white, or red light-emitting diode (LED) and were recorded from the visual cortex of the rats at various time points after the AAV vector injection. Chop2V fluorescence was predominantly observed in retinal ganglion cells (RGCs). Some fluorescence was observed in the inner nuclear layer and the inner plexiform layer neurites. A tendency of recovery was observed in the VEPs of aged RCS (rdy/rdy) rats after the AAV-Chop2V injection but not after the AAV-Venus injection. The visual response of AAV-Chop2V-injected aged RCS (rdy/rdy) rats was less sensitive to the blue LED flash than that of nondystrophic RCS (+/+) rats. The AAV-Chop2V-injected aged RCS (rdy/rdy) rats were insensitive to the red LED flash, which evoked a robust VEP in the RCS (+/+) rats. The visual response of aged RCS (rdy/rdy) rats was partially restored by transduction of the Chop2 gene through AAV into the inner retinal neurons, mainly RGCs. These results suggest that the transduction of Chop2 would provide a new strategy to treat some retinitis pigmentosa (RP) symptoms independent of their etiology.

The intra-individual reproducibility of flash-evoked potentials in a sample of children.

PubMed

Schellberg, D; Gasser, T; Köhler, W

1987-07-01

Visual evoked potentials (VEPs) to flash stimuli were recorded twice from 26 children aged 10-13 years, with an intersession interval of about 10 months. Test-retest reliability was poor for recordings taken from scalp locations overlying non-specific cortex and somewhat better for specific cortex. The size of consistency coefficients (i.e. correlations within session) showed that noise and artefacts were not the decisive factors which lower reliability. A comparison with retest correlations of broad band parameters of the EEG at rest for the same sample showed, to our surprise, smaller retest reliability for VEP parameters. Variability of the VEP in children over time seems to be a substantial as its well-known inter-individual variability.

Color blindness among multiple sclerosis patients in Isfahan.

PubMed

Shaygannejad, Vahid; Golabchi, Khodayar; Dehghani, Alireza; Ashtari, Fereshteh; Haghighi, Sepehr; Mirzendehdel, Mahsa; Ghasemi, Majid

2012-03-01

Multiple sclerosis (MS) is a disease of young and middle aged individuals with a demyelinative axonal damage nature in central nervous system that causes various signs and symptoms. As color vision needs normal function of optic nerve and macula, it is proposed that MS can alter it via influencing optic nerve. In this survey, we evaluated color vision abnormalities and its relationship with history of optic neuritis and abnormal visual evoked potentials (VEPs) among MS patients. The case group was included of clinically definitive MS patients and the same number of normal population was enrolled as the control group. Color vision of all the participants was evaluated by Ishihara test and then visual evoked potential (VEPs) and history of optic neuritis (ON) was assessed among them. Then, frequency of color blindness was compared between the case and the control group. Finally, color blinded patients were compared to those with the history of ON and abnormal VEPs. 63 MS patients and the same number of normal populations were enrolled in this study. 12 patients had color blindness based on the Ishihara test; only 3 of them were among the control group, which showed a significant different between the two groups (P = 0.013). There was a significant relationship between the color blindness and abnormal VEP (R = 0.53, P = 0.023) but not for the color blindness and ON (P = 0.67). This study demonstrates a significant correlation between color blindness and multiple sclerosis including ones with abnormal prolonged VEP latencies. Therefore, in individuals with acquired color vision impairment, an evaluation for potentially serious underlying diseases like MS is essential.

Influence of cataract surgery on optical coherence tomography and neurophysiology measurements in patients with retinitis pigmentosa.

PubMed

Garcia-Martin, Elena; Rodriguez-Mena, Diego; Dolz, Isabel; Almarcegui, Carmen; Gil-Arribas, Laura; Bambo, Maria P; Larrosa, Jose M; Polo, Vicente; Pablo, Luis E

2013-08-01

To evaluate the effect of uncomplicated cataract phacoemulsification on the measurements of visual evoked potentials (VEP), pattern electroretinogram (PERG), and macular and retinal nerve fiber layer (RNFL) using 2 spectral-domain optical coherence tomography (OCT) instruments, the Cirrus OCT (Carl Zeiss Meditech) and Spectralis OCT (Heidelberg Engineering), in patients with retinitis pigmentosa (RP), and to assess the reliability of the OCT measurements before and after cataract surgery. Observational cross-sectional study. Thirty-five eyes of 35 patients with RP (20 men and 15 women, 45-66 years) who underwent cataract phacoemulsification were studied. At 1 month before and 1 month after surgery, visual acuity, VEP, PERG, and 3 repetitions of scans using the RNFL and macular analysis protocols of the Cirrus and Spectralis OCT instruments were performed. The differences in measurements between the 2 visits were analyzed. Repeatability of OCT measurements was evaluated by calculating the coefficients of variation. VEP amplitude, RNFL thicknesses provided by Cirrus and Spectralis, and macular measurements provided by Cirrus OCT differed between the 2 visits. VEP latency, PERG measurements, and macular thicknesses provided by the Spectralis OCT before surgery did not differ significantly from those after surgery. The OCT repeatability was better after surgery, with lower coefficients of variation for scans performed after surgical removal of the cataract. The nuclear, cortical, and posterior subcapsular types of cataracts did not show different repeatability. The presence of cataracts affects VEP amplitude, RNFL, and macular measurements performed with OCT in eyes with RP. Image repeatability significantly improves after cataract phacoemulsification. Copyright © 2013 Elsevier Inc. All rights reserved.

Subclinical visual involvement in multiple sclerosis: a study by MRI, VEPs, frequency-doubling perimetry, standard perimetry, and contrast sensitivity.

PubMed

Sisto, Dario; Trojano, Maria; Vetrugno, Michele; Trabucco, Tiziana; Iliceto, Giovanni; Sborgia, Carlo

2005-04-01

To evaluate the effectiveness of visual evoked potentials (VEPs), frequency-doubling perimetry (FDP), standard achromatic perimetry (SAP), contrast sensitivity (CS) test, and magnetic resonance imaging (MRI), isolated or in combination, in detecting subclinical impairment of visual function in multiple sclerosis (MS). Twenty-two eyes of 11 patients affected by clinically definite MS, without a history of optic neuritis and asymptomatic for visual disturbances, underwent full ophthalmic examination and, in addition, VEPs, FDP, SAP, CS, and MRI. Abnormal results were taken to be as follows: for VEPs, a P100 latency >115 ms; for FDP, abnormal mean deviation (MD) or pattern SD (PSD); for SAP, abnormal MD or PSD; for CS, abnormal CS at one spatial frequency, at least; and for MRI, evidence of at least one demyelinating plaque along the visual pathway. VEPs showed abnormal results in 12 eyes (54.4%), FDP in 11 (50%), SAP in 14 (63.6%), CS in 17 (77.1%), and MRI in 16 (72.7%). In only two (9.1%) eyes of the same patient was no abnormality found. No single test detected all the abnormal eyes. Four (18.2%) eyes had pure optic nerve involvement and the remaining 16 (72.7%) had both pre- and postchiasmal involvement. In patients affected by clinically definite MS without history of optic neuritis and no visual symptoms, there is a large prevalence of visual pathway involvement that can be diagnosed only by performing multiple tests. The comparison of the tests is also useful to detect the presence of multiple lesions in the same patient.

Flash visual evoked potentials in patients with periventricular leucomalacia in children less than 1 year of age.

PubMed

Jethani, Jitendra; Jethani, Monika

2013-11-01

Children with periventricular leucomalacia (PVL) are known to have visual impairment of various forms starting from reduced vision, field defects, congnitive problems, and problems with hand eye coordination. There is very scant data/literature on the visual evoked potentials (VEPs) at an early age in children with PVL. We did a study to evaluate the flash visual evoked potentials (fVEPs) in children with PVL less than 1 year of age. A total of nine children diagnosed as having PVL on magnetic resonance imaging were included in the study. The mean age was 9.7μ 3.5 months. All children underwent handheld fVEPs under sedation at two different flash frequencies 1.4 and 8 Hz. The mean latency of N1 and P1 on stimulation with 1.4 Hz was 47.9μ 15.2 and 77.7μ 26.0 ms, respectively. However, on stimulation with 8 Hz the mean latency of N1 and P1 was 189.8μ 25.6 and 238.4μ 33.6 ms, respectively. The mean amplitude with 1.4 Hz and 8 stimulation frequency was 5.6μ 4.5 and 5.59μ 3 mV, respectively. We have found for the first time that there is a change in the latency and the delay occurs at 8 Hz frequency but not at 1.4 Hz. We also conclude that amplitudes by fVEPs may be normal even in presence of periventricular changes. The amplitudes of fVEPs are not reliable in children with PVL.

Impaired early visual response modulations to spatial information in chronic schizophrenia

PubMed Central

Knebel, Jean-François; Javitt, Daniel C.; Murray, Micah M.

2011-01-01

Early visual processing stages have been demonstrated to be impaired in schizophrenia patients and their first-degree relatives. The amplitude and topography of the P1 component of the visual evoked potential (VEP) are both affected; the latter of which indicates alterations in active brain networks between populations. At least two issues remain unresolved. First, the specificity of this deficit (and suitability as an endophenotype) has yet to be established, with evidence for impaired P1 responses in other clinical populations. Second, it remains unknown whether schizophrenia patients exhibit intact functional modulation of the P1 VEP component; an aspect that may assist in distinguishing effects specific to schizophrenia. We applied electrical neuroimaging analyses to VEPs from chronic schizophrenia patients and healthy controls in response to variation in the parafoveal spatial extent of stimuli. Healthy controls demonstrated robust modulation of the VEP strength and topography as a function of the spatial extent of stimuli during the P1 component. By contrast, no such modulations were evident at early latencies in the responses from patients with schizophrenia. Source estimations localized these deficits to the left precuneus and medial inferior parietal cortex. These findings provide insights on potential underlying low-level impairments in schizophrenia. PMID:21764264

Electrophysiological assessment in patients with long term hypoxia.

PubMed

Ilik, Faik; Pazarli, Ahmet C; Kayhan, Fatih; Karamanli, Harun; Ozlece, Hatice K

2016-01-01

To evaluate visual evoked potentials (VEP) patterns in chronic obstructive pulmonary disease (COPD) patients who were compliant with supplemental oxygen treatment relative to non-compliant COPD patients. This prospective study protocol was reviewed and approved by the local ethical committee of Selcuk University and the research was performed in the Department of Neurology, Elbistan State Hospital, Kahramanmaras, Turkey from May to October 2014. Blood gas measurements and pulmonary function tests were carried out in patients with advanced stage COPD. The VEP was assessed in both eyes in both compliant and non-compliant patients. The study included 43 patients; 24 (55.8%) of the patients were not in compliance with their supplemental oxygen treatment, while 19 patients (44.2%) received adequate oxygen treatment. There was no statistically significant difference between patients with regards to pulmonary function test results and blood gas measurements. The VEP latency was significantly greater in both eyes of the non-compliant patients. Previous studies have reported prolonged VEP latencies in inflammatory diseases of the central nervous system. Similar electrophysiological findings were observed in our study and we propose that this may be due to oxidative stress, and inflammation that occurs secondary to chronic ischemia.

Oscillatory encoding of visual stimulus familiarity.

PubMed

Kissinger, Samuel T; Pak, Alexandr; Tang, Yu; Masmanidis, Sotiris C; Chubykin, Alexander A

2018-06-18

Familiarity of the environment changes the way we perceive and encode incoming information. However, the neural substrates underlying this phenomenon are poorly understood. Here we describe a new form of experience-dependent low frequency oscillations in the primary visual cortex (V1) of awake adult male mice. The oscillations emerged in visually evoked potentials (VEPs) and single-unit activity following repeated visual stimulation. The oscillations were sensitive to the spatial frequency content of a visual stimulus and required the muscarinic acetylcholine receptors (mAChRs) for their induction and expression. Finally, ongoing visually evoked theta (4-6 Hz) oscillations boost the VEP amplitude of incoming visual stimuli if the stimuli are presented at the high excitability phase of the oscillations. Our results demonstrate that an oscillatory code can be used to encode familiarity and serves as a gate for oncoming sensory inputs. Significance Statement. Previous experience can influence the processing of incoming sensory information by the brain and alter perception. However, the mechanistic understanding of how this process takes place is lacking. We have discovered that persistent low frequency oscillations in the primary visual cortex encode information about familiarity and the spatial frequency of the stimulus. These familiarity evoked oscillations influence neuronal responses to the oncoming stimuli in a way that depends on the oscillation phase. Our work demonstrates a new mechanism of visual stimulus feature detection and learning. Copyright © 2018 the authors.

Emotional facial expressions reduce neural adaptation to face identity.

PubMed

Gerlicher, Anna M V; van Loon, Anouk M; Scholte, H Steven; Lamme, Victor A F; van der Leij, Andries R

2014-05-01

In human social interactions, facial emotional expressions are a crucial source of information. Repeatedly presented information typically leads to an adaptation of neural responses. However, processing seems sustained with emotional facial expressions. Therefore, we tested whether sustained processing of emotional expressions, especially threat-related expressions, would attenuate neural adaptation. Neutral and emotional expressions (happy, mixed and fearful) of same and different identity were presented at 3 Hz. We used electroencephalography to record the evoked steady-state visual potentials (ssVEP) and tested to what extent the ssVEP amplitude adapts to the same when compared with different face identities. We found adaptation to the identity of a neutral face. However, for emotional faces, adaptation was reduced, decreasing linearly with negative valence, with the least adaptation to fearful expressions. This short and straightforward method may prove to be a valuable new tool in the study of emotional processing.

When "Veps" Cry: Two-Year-Olds Efficiently Learn Novel Words from Linguistic Contexts Alone

ERIC Educational Resources Information Center

Ferguson, Brock; Graf, Eileen; Waxman, Sandra R.

2018-01-01

We assessed 24-month-old infants' lexical processing efficiency for both novel and familiar words. Prior work documented that 19-month-olds successfully identify referents of familiar words (e.g., The dog is so little) as well as novel words whose meanings were informed only by the surrounding sentence (e.g., The vep is crying), but that the speed…

Volumetric electromagnetic phase-shift spectroscopy of brain edema and hematoma.

PubMed

Gonzalez, Cesar A; Valencia, Jose A; Mora, Alfredo; Gonzalez, Fernando; Velasco, Beatriz; Porras, Martin A; Salgado, Javier; Polo, Salvador M; Hevia-Montiel, Nidiyare; Cordero, Sergio; Rubinsky, Boris

2013-01-01

Motivated by the need of poor and rural Mexico, where the population has limited access to advanced medical technology and services, we have developed a new paradigm for medical diagnostic based on the technology of "Volumetric Electromagnetic Phase Shift Spectroscopy" (VEPS), as an inexpensive partial substitute to medical imaging. VEPS, can detect changes in tissue properties inside the body through non-contact, multi-frequency electromagnetic measurements from the exterior of the body, and thereby provide rapid and inexpensive diagnostics in a way that is amenable for use in economically disadvantaged parts of the world. We describe the technology and report results from a limited pilot study with 46 healthy volunteers and eight patients with CT radiology confirmed brain edema and brain hematoma. Data analysis with a non-parametric statistical Mann-Whitney U test, shows that in the frequency range of from 26 MHz to 39 MHz, VEPS can distinguish non-invasively and without contact, with a statistical significance of p<0.05, between healthy subjects and those with a medical conditions in the brain. In the frequency range of between 153 MHz to 166 MHz it can distinguish with a statistical significance of p<0.05 between subjects with brain edema and those with a hematoma in the brain. A classifier build from measurements in these two frequency ranges can provide instantaneous diagnostic of the medical condition of the brain of a patient, from a single set of measurements. While this is a small-scale pilot study, it illustrates the potential of VEPS to change the paradigm of medical diagnostic of brain injury through a VEPS classifier-based technology. Obviously substantially larger-scale studies are needed to verify and expand on the findings in this small pilot study.

Volumetric Electromagnetic Phase-Shift Spectroscopy of Brain Edema and Hematoma

PubMed Central

Gonzalez, Cesar A.; Valencia, Jose A.; Mora, Alfredo; Gonzalez, Fernando; Velasco, Beatriz; Porras, Martin A.; Salgado, Javier; Polo, Salvador M.; Hevia-Montiel, Nidiyare; Cordero, Sergio; Rubinsky, Boris

2013-01-01

Motivated by the need of poor and rural Mexico, where the population has limited access to advanced medical technology and services, we have developed a new paradigm for medical diagnostic based on the technology of “Volumetric Electromagnetic Phase Shift Spectroscopy” (VEPS), as an inexpensive partial substitute to medical imaging. VEPS, can detect changes in tissue properties inside the body through non-contact, multi-frequency electromagnetic measurements from the exterior of the body, and thereby provide rapid and inexpensive diagnostics in a way that is amenable for use in economically disadvantaged parts of the world. We describe the technology and report results from a limited pilot study with 46 healthy volunteers and eight patients with CT radiology confirmed brain edema and brain hematoma. Data analysis with a non-parametric statistical Mann-Whitney U test, shows that in the frequency range of from 26 MHz to 39 MHz, VEPS can distinguish non-invasively and without contact, with a statistical significance of p<0.05, between healthy subjects and those with a medical conditions in the brain. In the frequency range of between 153 MHz to 166 MHz it can distinguish with a statistical significance of p<0.05 between subjects with brain edema and those with a hematoma in the brain. A classifier build from measurements in these two frequency ranges can provide instantaneous diagnostic of the medical condition of the brain of a patient, from a single set of measurements. While this is a small-scale pilot study, it illustrates the potential of VEPS to change the paradigm of medical diagnostic of brain injury through a VEPS classifier-based technology. Obviously substantially larger-scale studies are needed to verify and expand on the findings in this small pilot study. PMID:23691001

Pattern visual evoked potentials elicited by organic electroluminescence screen.

PubMed

Matsumoto, Celso Soiti; Shinoda, Kei; Matsumoto, Harue; Funada, Hideaki; Sasaki, Kakeru; Minoda, Haruka; Iwata, Takeshi; Mizota, Atsushi

2014-01-01

To determine whether organic electroluminescence (OLED) screens can be used as visual stimulators to elicit pattern-reversal visual evoked potentials (p-VEPs). Checkerboard patterns were generated on a conventional cathode-ray tube (S710, Compaq Computer Co., USA) screen and on an OLED (17 inches, 320 × 230 mm, PVM-1741, Sony, Tokyo, Japan) screen. The time course of the luminance changes of each monitor was measured with a photodiode. The p-VEPs elicited by these two screens were recorded from 15 eyes of 9 healthy volunteers (22.0 ± 0.8 years). The OLED screen had a constant time delay from the onset of the trigger signal to the start of the luminescence change. The delay during the reversal phase from black to white for the pattern was 1.0 msec on the cathode-ray tube (CRT) screen and 0.5 msec on the OLED screen. No significant differences in the amplitudes of P100 and the implicit times of N75 and P100 were observed in the p-VEPs elicited by the CRT and the OLED screens. The OLED screen can be used as a visual stimulator to elicit p-VEPs; however the time delay and the specific properties in the luminance change must be taken into account.

Visual and brainstem auditory evoked potentials in children with obesity.

PubMed

Akın, Onur; Arslan, Mutluay; Akgün, Hakan; Yavuz, Süleyman Tolga; Sarı, Erkan; Taşçılar, Mehmet Emre; Ulaş, Ümit Hıdır; Yeşilkaya, Ediz; Ünay, Bülent

2016-03-01

The aim of our study is to investigate alterations in visual evoked potentials (VEP) and brainstem auditory evoked potentials (BAEP) in children with obesity. A total of 96 children, with a mean age of 12.1±2.0 years (range 9-17 years, 63 obese and 33 age and sex-matched control subjects) were included in the study. Laboratory tests were performed to detect insulin resistance (IR) and dyslipidemia. The latencies and amplitudes of VEP and BAEP were measured in healthy and obese subjects. The VEP P100, BAEP interpeak latency (IPL) I-III and IPL I-V averages of obese children were significantly longer than the control subjects. When the obese group was divided into two subgroups, those with IR and without IR, BAEP wave I, wave III and P100 wave latencies were found to be longer in the group with IR. A statistically significant correlation was observed between BAEP wave I latency, IPL I-V, IPL I-III and the homeostatic model assessment insulin resistance (HOMA IR) index and fasting insulin level. Our findings suggest that VEP and BAEP can be used to determine early subclinical on auditory and visual functions of obese children with insulin resistance. Copyright © 2015 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Visual Evoked Potential to Assess Retinopathy in Gestational Diabetes Mellitus.

PubMed

Hari Kumar, K V S; Ahmad, F M H; Sood, Sandeep; Mansingh, Sudhir

2016-04-01

We evaluated for early retinopathy using the visual evoked potential (VEP) in patients with gestational diabetes mellitus (GDM) and type 2 diabetes mellitus during pregnancy. All patients with GDM and type 2 diabetes seen between June and October of 2014 were included in this cross-sectional, observational study. Patients with secondary diabetes, ocular or major illness were excluded from the study. VEP was recorded in both eyes to derive prominent positive peak latency (P100), amplitude and initial negative deflection (N75) latency. The data were compared with 10 gestational age-matched controls with normal glucose tolerance. Appropriate statistical methods were used for comparison among the 3 groups. The study participants (40 with GDM, 10 with type 2 diabetes, 10 with normal glucose tolerance) had a median (25th to 75th interquartile range) age of 26 (24.3, 30) years, a gestational age of 24.5 (21, 27) weeks and weights of 66.8 (63.4, 71.5) kg. The P100 latencies were comparable among the 3 groups (p=0.0577). However, patients with any diabetes (GDM and type 2 diabetes) had prolonged P100 latencies (p=0.0139) and low P100 amplitudes (p=0.0391) in comparison to controls. P100 latency showed a direct correlation with hyperglycemia (p=0.0118). Our data showed that VEP abnormalities are detectable even in the short-term hyperglycemia of GDM and type 2 diabetes. Copyright © 2016 Canadian Diabetes Association. Published by Elsevier Inc. All rights reserved.

Initial neuro-ophthalmological manifestations in Churg–Strauss syndrome

PubMed Central

Vallet, Anne-Evelyne; Didelot, Adrien; Guebre-Egziabher, Fitsum; Bernard, Martine; Mauguière, François

2010-01-01

Churg–Strauss syndrome (CSS) is a systemic vasculitis with frequent respiratory tract involvement. It can also affect the nervous system, notably the optic tract. The present work reports the case of a 65-year-old man diagnosed as having CSS in the context of several acute onset neurological symptoms including muscle weakness and signs of temporal arteritis, including bilateral anterior ischaemic optic neuropathy (ON). Electroretinograms (ERGs) and visual evoked potentials (VEPs) were performed. Flash ERGs were normal whereas VEPs were highly abnormal, showing a dramatic voltage reduction, thus confirming the ON. The vision outcome was poor. Ophthalmological presentations of CSS have rarely been reported, but no previous case of sudden blindness documented by combined ERG and VEP investigations were found in the literature. The present case strongly suggests that the occurrence of visual loss in the context of systemic inflammation with hypereosinophilia should lead to considering the diagnosis of CSS. PMID:22789694

Visual evoked potentials and selective attention to points in space

NASA Technical Reports Server (NTRS)

Van Voorhis, S.; Hillyard, S. A.

1977-01-01

Visual evoked potentials (VEPs) were recorded to sequences of flashes delivered to the right and left visual fields while subjects responded promptly to designated stimuli in one field at a time (focused attention), in both fields at once (divided attention), or to neither field (passive). Three stimulus schedules were used: the first was a replication of a previous study (Eason, Harter, and White, 1969) where left- and right-field flashes were delivered quasi-independently, while in the other two the flashes were delivered to the two fields in random order (Bernoulli sequence). VEPs to attended-field stimuli were enhanced at both occipital (O2) and central (Cz) recording sites under all stimulus sequences, but different components were affected at the two scalp sites. It was suggested that the VEP at O2 may reflect modality-specific processing events, while the response at Cz, like its auditory homologue, may index more general aspects of selective attention.

Pattern Visual Evoked Potential as a Predictor of Occlusion Therapy for Amblyopia

PubMed Central

Chung, Woosuk; Hong, Samin; Lee, Jong Bok

2008-01-01

Purpose This study was conducted to investigate the role of the pattern visual evoked potential (pVEP) as a predictor of occlusion therapy for patients with strabismic, anisometropic, and isometropic amblyopia. The secondary aim was to compare the characteristics of pVEP between strabismic and anisometropic amblyopia. Methods This retrospective comparative case series included 120 patients who had received occlusion therapy or a glasses prescription for correction of strabismic, anisometropic, and isometropic amblyopia (20 patients had strabismic amblyopia, 41 patients had anisometropic amblyopia, and 59 patients had isometropic amblyopia). For each patient, the value of the P100 latency on pVEP at the time of the initial diagnosis of amblyopia was collected. Subsequently, the P100 latency was compared according to types of amblyopia. Fifty of 120 patients (7 patients with strabismic amblyopia, 21 patients with anisometropic amblyopia, and 22 patients with isometropic amblyopia) who were followed-up for longer than 6 months were divided into two groups based on the value of their P100 latency (Group 1, P100 latency 120 msec or less; Group 2, P100 latency longer than 120 msec.) The amount of visual improvement after occlusion therapy or glasses was compared between two study groups. Results The mean P100 latency was 119.7±25.2 msec in eyes with strabismic amblyopia and 111.9±17.8 msec in eyes with non-strabismic (anisometropic or isometropic) amblyopia (p=0.213). In Group 1, the mean visual improvement after occlusion therapy or glasses was 3.69±2.14 lines on Dr. Hahn's standard test chart; in Group 2, the mean improvement was 2.27±2.21 lines (p=0.023). Conclusions The P100 latency on pVEP at the time of initial diagnosis was significantly related to the visual improvement after occlusion therapy or glasses in patients with strabismic, anisometropic, and isometropic amblyopia. Therefore, it was presumed that patients with a delayed P100 latency might have less visual improvement after occlusion therapy or glasses. In addition, there was no apparent difference in P100 latency between patients with strabismic and non-strabismic (anisometropic or isometropic) amblyopia. PMID:19096243

The effect of transcranial direct current stimulation on contrast sensitivity and visual evoked potential amplitude in adults with amblyopia

PubMed Central

Ding, Zhaofeng; Li, Jinrong; Spiegel, Daniel P.; Chen, Zidong; Chan, Lily; Luo, Guangwei; Yuan, Junpeng; Deng, Daming; Yu, Minbin; Thompson, Benjamin

2016-01-01

Amblyopia is a neurodevelopmental disorder of vision that occurs when the visual cortex receives decorrelated inputs from the two eyes during an early critical period of development. Amblyopic eyes are subject to suppression from the fellow eye, generate weaker visual evoked potentials (VEPs) than fellow eyes and have multiple visual deficits including impairments in visual acuity and contrast sensitivity. Primate models and human psychophysics indicate that stronger suppression is associated with greater deficits in amblyopic eye contrast sensitivity and visual acuity. We tested whether transcranial direct current stimulation (tDCS) of the visual cortex would modulate VEP amplitude and contrast sensitivity in adults with amblyopia. tDCS can transiently alter cortical excitability and may influence suppressive neural interactions. Twenty-one patients with amblyopia and twenty-seven controls completed separate sessions of anodal (a-), cathodal (c-) and sham (s-) visual cortex tDCS. A-tDCS transiently and significantly increased VEP amplitudes for amblyopic, fellow and control eyes and contrast sensitivity for amblyopic and control eyes. C-tDCS decreased VEP amplitude and contrast sensitivity and s-tDCS had no effect. These results suggest that tDCS can modulate visual cortex responses to information from adult amblyopic eyes and provide a foundation for future clinical studies of tDCS in adults with amblyopia. PMID:26763954

The effect of transcranial direct current stimulation on contrast sensitivity and visual evoked potential amplitude in adults with amblyopia.

PubMed

Ding, Zhaofeng; Li, Jinrong; Spiegel, Daniel P; Chen, Zidong; Chan, Lily; Luo, Guangwei; Yuan, Junpeng; Deng, Daming; Yu, Minbin; Thompson, Benjamin

2016-01-14

Amblyopia is a neurodevelopmental disorder of vision that occurs when the visual cortex receives decorrelated inputs from the two eyes during an early critical period of development. Amblyopic eyes are subject to suppression from the fellow eye, generate weaker visual evoked potentials (VEPs) than fellow eyes and have multiple visual deficits including impairments in visual acuity and contrast sensitivity. Primate models and human psychophysics indicate that stronger suppression is associated with greater deficits in amblyopic eye contrast sensitivity and visual acuity. We tested whether transcranial direct current stimulation (tDCS) of the visual cortex would modulate VEP amplitude and contrast sensitivity in adults with amblyopia. tDCS can transiently alter cortical excitability and may influence suppressive neural interactions. Twenty-one patients with amblyopia and twenty-seven controls completed separate sessions of anodal (a-), cathodal (c-) and sham (s-) visual cortex tDCS. A-tDCS transiently and significantly increased VEP amplitudes for amblyopic, fellow and control eyes and contrast sensitivity for amblyopic and control eyes. C-tDCS decreased VEP amplitude and contrast sensitivity and s-tDCS had no effect. These results suggest that tDCS can modulate visual cortex responses to information from adult amblyopic eyes and provide a foundation for future clinical studies of tDCS in adults with amblyopia.

Effects of hyper +Gz acceleration on cardiovascular function, visual evoked potentials and cerebral blood flow in anesthetized rats.

PubMed

Matsunami, K; Satake, H; Konishi, T

1998-07-01

Sustained hyper-gravity acceleration, particularly along the long axis of the body of animals or man (Gz), produces significant mal-effects on subjects, and hence it has been well studied, The most common syndromes of Gz application were cardio-vascular de-conditioning, and black-out, red-out, and loss of consciousness, which finally lead subjects into death. However, in most previous studies, the duration of applied Gz was rather short. In the present experiments, we can use longer duration of 1000 seconds. In addition, recent technological innovation make it possible to record directly local cerebral blood flow at a target cortical area with a Laser Doppler flow meter. We used this innovated method to measure local cerebral blood flow of rats in relation to visual evoked potentials (VEPs) under hyper-Gz acceleration. Also we recorded cardio-vascular parameters like heart rate from ECG, systolic and diastolic blood pressure and correlated them with cerebral blood flow and VEPs.

Lateral geniculate body evoked potentials elicited by visual and electrical stimulation.

PubMed

Choi, Chang Wook; Kim, Pan Sang; Shin, Sun Ae; Yang, Ji Yeon; Yang, Yun Sik

2014-08-01

Blind individuals who have photoreceptor loss are known to perceive phosphenes with electrical stimulation of their remaining retinal ganglion cells. We proposed that implantable lateral geniculate body (LGB) stimulus electrode arrays could be used to generate phosphene vision. We attempted to refine the basic reference of the electrical evoked potentials (EEPs) elicited by microelectrical stimulations of the optic nerve, optic tract and LGB of a domestic pig, and then compared it to visual evoked potentials (VEPs) elicited by short-flash stimuli. For visual function measurement, VEPs in response to short-flash stimuli on the left eye of the domestic pig were assessed over the visual cortex at position Oz with the reference electrode at Fz. After anesthesia, linearly configured platinum wire electrodes were inserted into the optic nerve, optic track and LGB. To determine the optimal stimulus current, EEPs were recorded repeatedly with controlling the pulse and power. The threshold of current and charge density to elicit EEPs at 0.3 ms pulse duration was about ±10 µA. Our experimental results showed that visual cortex activity can be effectively evoked by stimulation of the optic nerve, optic tract and LGB using penetrating electrodes. The latency of P1 was more shortened as the electrical stimulation was closer to LGB. The EEPs of two-channel in the visual cortex demonstrated a similar pattern with stimulation of different spots of the stimulating electrodes. We found that the LGB-stimulated EEP pattern was very similar to the simultaneously generated VEP on the control side, although implicit time deferred. EEPs and VEPs derived from visual-system stimulation were compared. The LGB-stimulated EEP wave demonstrated a similar pattern to the VEP waveform except implicit time, indicating prosthetic-based electrical stimulation of the LGB could be utilized for the blind to perceive vision of phosphenes.

Visual abnormalities associated with enhanced optic nerve myelination.

PubMed

Yu, Minzhong; Narayanan, S Priyadarshini; Wang, Feng; Morse, Emily; Macklin, Wendy B; Peachey, Neal S

2011-02-16

Expression of the constitutively active serine/threonine kinase Akt in oligodendrocytes results in enhanced myelination in the CNS. Here, we have examined the effects of this Akt overexpression on optic nerve structure and on optic nerve function, assessed using the visual evoked potential (VEP). Transgenic mice have been generated with the Plp promoter driving expression of a modified form of Akt, in which aspartic acids are substituted for Thr308 and Ser473. These Plp-Akt-DD (Akt-DD) mice, and littermate controls, were studied at different ages. Optic nerves were examined anatomically at 2 and 6 months of age. At 2 months of age, optic nerves were substantially thicker in Akt-DD mice, reflecting an increase in myelination of optic nerve axons. By electron microscopy, myelin thickness was increased in Akt-DD optic nerve, with extended paranodal domains having excess paranodal loops, and the density of nodes of Ranvier was reduced, relative to control mice. We recorded VEPs in response to strobe flash ganzfeld stimuli presented after overnight dark- and light-adapted conditions at ages ranging from 1 to 10 months. It was possible to record a clear VEP from Akt-DD mice at all ages examined. At 1 month of age, VEP implicit times were somewhat shorter in Akt-DD transgenic mice than in control animals. Beyond 6months of age, VEP latencies were consistently delayed in Akt-DD transgenic mice. These abnormalities did not reflect an alteration in retinal function as there were no significant differences between ERGs obtained from control or Akt-DD transgenic mice. In young mice, the somewhat faster responses may reflect improved transmission due to increased myelination of optic nerve axons. In older mice, where the Akt-DD optic nerve is markedly thicker than control, it is remarkable that optic nerves continue to function. Copyright © 2010 Elsevier B.V. All rights reserved.

Interactions of Prosthetic and Natural Vision in Animals With Local Retinal Degeneration

PubMed Central

Lorach, Henri; Lei, Xin; Galambos, Ludwig; Kamins, Theodore; Mathieson, Keith; Dalal, Roopa; Huie, Philip; Harris, James; Palanker, Daniel

2015-01-01

Purpose Prosthetic restoration of partial sensory loss leads to interactions between artificial and natural inputs. Ideally, the rehabilitation should allow perceptual fusion of the two modalities. Here we studied the interactions between normal and prosthetic vision in a rodent model of local retinal degeneration. Methods Implantation of a photovoltaic array in the subretinal space of normally sighted rats induced local degeneration of the photoreceptors above the chip, and the inner retinal neurons in this area were electrically stimulated by the photovoltaic implant powered by near-infrared (NIR) light. We studied prosthetic and natural visually evoked potentials (VEP) in response to simultaneous stimulation by NIR and visible light patterns. Results We demonstrate that electrical and natural VEPs summed linearly in the visual cortex, and both responses decreased under brighter ambient light. Responses to visible light flashes increased over 3 orders of magnitude of contrast (flash/background), while for electrical stimulation the contrast range was limited to 1 order of magnitude. The maximum amplitude of the prosthetic VEP was three times lower than the maximum response to a visible flash over the same area on the retina. Conclusions Ambient light affects prosthetic responses, albeit much less than responses to visible stimuli. Prosthetic representation of contrast in the visual scene can be encoded, to a limited extent, by the appropriately calibrated stimulus intensity, which also depends on the ambient light conditions. Such calibration will be important for patients combining central prosthetic vision with natural peripheral sight, such as in age-related macular degeneration. PMID:26618643

EEG Analysis of the Effects of Therapeutic Cooling on the Cognitive Performance of Multiple Sclerosis Patients

NASA Technical Reports Server (NTRS)

Montgomery, Leslie D.; Montgomery, Richard W.; Ku, Yu-Tsuan E.; Luna, Bernadette; Lee, Hank C.; Kliss, Mark; Webbon, Bruce; Mead, Susan C. (Technical Monitor)

1999-01-01

The objective of this project was to determine whether a controlled period of head and torso cooling would enhance the cognitive performance of multiple sclerosis patients. Nineteen MS patients (11 men and 8 women) participated in the study. Control data were taken from nineteen healthy volunteers (12 men and 7 women). All but six of nineteen MS patients tested improved their cognitive performance, as measured by their scores on the Rao test battery. A second objective was to gain insight into the neurological effects of cooling. Visual evoked potentials (VEPs) stimulated by a reversing checkerboard pattern were recorded before and after cooling. We found that cooling selectively benefited the cognitive performance of those MS patients whose pre-cooling VEPs were abnormally shaped (which is an indication of visual pathway impairment due to demyelinization). Moreover, for female MS patients, the degree of cognitive performance improvement following cooling was correlated with a change in the shape of their VEPs toward a more normal shape following cooling.

Influence of P300 latency jitter on event related potential-based brain-computer interface performance

NASA Astrophysics Data System (ADS)

Aricò, P.; Aloise, F.; Schettini, F.; Salinari, S.; Mattia, D.; Cincotti, F.

2014-06-01

Objective. Several ERP-based brain-computer interfaces (BCIs) that can be controlled even without eye movements (covert attention) have been recently proposed. However, when compared to similar systems based on overt attention, they displayed significantly lower accuracy. In the current interpretation, this is ascribed to the absence of the contribution of short-latency visual evoked potentials (VEPs) in the tasks performed in the covert attention modality. This study aims to investigate if this decrement (i) is fully explained by the lack of VEP contribution to the classification accuracy; (ii) correlates with lower temporal stability of the single-trial P300 potentials elicited in the covert attention modality. Approach. We evaluated the latency jitter of P300 evoked potentials in three BCI interfaces exploiting either overt or covert attention modalities in 20 healthy subjects. The effect of attention modality on the P300 jitter, and the relative contribution of VEPs and P300 jitter to the classification accuracy have been analyzed. Main results. The P300 jitter is higher when the BCI is controlled in covert attention. Classification accuracy negatively correlates with jitter. Even disregarding short-latency VEPs, overt-attention BCI yields better accuracy than covert. When the latency jitter is compensated offline, the difference between accuracies is not significant. Significance. The lower temporal stability of the P300 evoked potential generated during the tasks performed in covert attention modality should be regarded as the main contributing explanation of lower accuracy of covert-attention ERP-based BCIs.

Optimization of visual evoked potential (VEP) recording systems.

PubMed

Karanjia, Rustum; Brunet, Donald G; ten Hove, Martin W

2009-01-01

To explore the influence of environmental conditions on pattern visual evoked potential (VEP) recordings. Fourteen subjects with no known ocular pathology were recruited for the study. In an attempt to optimize the recording conditions, VEP recordings were performed in both the seated and recumbent positions. Comparisons were made between recordings using either LCD or CRT displays and recordings obtained in silence or with quiet background music. Paired recordings (in which only one variable was changed) were analyzed for changes in P100 latency, RMS noise, and variability. Baseline RMS noise demonstrated a significant decrease in the variability during the first 50msec accompanied by a 73% decrease in recording time for recumbent position when compared to the seated position (p<0.05). Visual evoked potentials recorded using LCD monitors demonstrated a significant increase in the P100 latency when compared to CRT recordings in the same subjects. The addition of background music did not affect the amount of RMS noise during the first 50msec of the recordings. This study demonstrates that the use of the recumbent position increases patient comfort and improves the signal to noise ratio. In contrast, the addition of background music to relax the patient did not improve the recording signal. Furthermore, the study illustrates the importance of avoiding low-contrast visual stimulation patterns obtained with LCD as they lead to higher latencies resulting in false positive recordings. These findings are important when establishing or modifying a pattern VEP recording protocol.

Sustained neuroprotection from a single intravitreal injection of PGJ2 in a rodent model of anterior ischemic optic neuropathy.

PubMed

Touitou, Valerie; Johnson, Mary A; Guo, Yan; Miller, Neil R; Bernstein, Steven L

2013-11-11

Nonarteritic anterior ischemic optic neuropathy (NAION) is the most common cause of sudden optic nerve-related vision loss in persons older than 50 in the United States. There currently is no treatment for this disorder. We previously showed that systemic administration of 15-deoxy, delta (12, 14) prostaglandin J2 (PGJ2) is neuroprotective in our rodent model of AION (rAION). In this study, we determined if a single intravitreal (IVT) injection of PGJ2 is neuroprotective after rAION, and if this method of administration is toxic to the retina, optic nerve, or both. TOXICITY was assessed after a single IVT injection of PGJ2 in one eye and PBS in the contralateral eye of normal, adult Long-Evans rats. EFFICACY was assessed by inducing rAION in one eye and injecting either PGJ2 or vehicle immediately following induction, with the fellow eye serving as naïve control. Visual evoked potentials (VEPs) and ERGs were performed before induction and at specific intervals thereafter. Animals were euthanized 30 days after induction, after which immunohistochemistry, transmission electron microscopy, and quantitative stereology of retinal ganglion cell (RGC) numbers were performed. IVT PGJ2 did not alter the VEP or ERG compared with PBS-injected control eyes, and neither IVT PGJ2 nor PBS reduced overall RGC numbers. IVT PGJ2 preserved VEP amplitude, reduced optic nerve edema, and resulted in significant preservation of RGCs and axons in eyes with rAION. A single IVT injection of PGJ2 is nontoxic to the retina and optic nerve and neuroprotective when given immediately after rAION induction.

Effect of hyperbaric oxygen on lipid peroxidation and visual development in neonatal rats with hypoxia-ischemia brain damage.

PubMed

Chen, Jing; Chen, Yan-Hui; Lv, Hong-Yan; Chen, Li-Ting

2016-07-01

The aim of the present study was to investigate the effect of hyperbaric oxygen (HBO) on lipid peroxidation and visual development in a neonatal rat model of hypoxic-ischemic brain damage (HIBD). The rat models of HIBD were established by delayed uterus dissection and were divided randomly into two groups (10 rats each): HIBD and HBO-treated HIBD (HIBD+HBO) group. Another 20 rats that underwent sham-surgery were also divided randomly into the HBO-treated and control groups. The rats that underwent HBO treatment received HBO (0.02 MPa, 1 h/day) 24 h after the surgery and this continued for 14 days. When rats were 4 weeks old, their flash visual evoked potentials (F-VEPs) were monitored and the ultrastructures of the hippocampus were observed under transmission electron microscope. The levels of superoxide dismutase (SOD) and malonyldialdehyde (MDA) in the brain tissue homogenate were detected by xanthine oxidase and the thiobarbituric acid colorimetric method. Compared with the control group, the ultrastructures of the pyramidal neurons in the hippocampal CA3 area were distorted, the latencies of F-VEPs were prolonged (P<0.01) and the SOD activities were lower while the MDA levels were higher (P<0.01) in the HIBD group. No significant differences in ultrastructure, the latency of F-VEPs or SOD/MDA levels were identified between the HBO-treated HIBD group and the normal control group (P>0.05). HBO enhances antioxidant capacity and reduces the ultrastructural damage induced by hypoxic-ischemia, which may improve synaptic reconstruction and alleviate immature brain damage to promote the habilitation of brain function.

Elaborate mapping of the posterior visual pathway in awake craniotomy.

PubMed

Shahar, Tal; Korn, Akiva; Barkay, Gal; Biron, Tali; Hadanny, Amir; Gazit, Tomer; Nossek, Erez; Ekstein, Margaret; Kesler, Anat; Ram, Zvi

2018-05-01

OBJECTIVE Resection of intraaxial tumors adjacent to the optic radiation (OR) may be associated with postoperative visual field (VF) deficits. Intraoperative navigation using MRI-based tractography and electrophysiological monitoring of the visual pathways may allow maximal resection while preserving visual function. In this study, the authors evaluated the value of visual pathway mapping in a series of patients undergoing awake craniotomy for tumor resection. METHODS A retrospective analysis of prospectively collected data was conducted in 18 patients who underwent an awake craniotomy for resection of intraaxial tumors involving or adjacent to the OR. Preoperative MRI-based tractography was used for intraoperative navigation, and intraoperative acquisition of 3D ultrasonography images was performed for real-time imaging and correction of brain shift. Goggles with light-emitting diodes were used as a standard visual stimulus. Direct cortical visual evoked potential (VEP) recording, subcortical recordings from the OR, and subcortical stimulation of the OR were used intraoperatively to assess visual function and proximity of the lesion to the OR. VFs were assessed pre- and postoperatively. RESULTS Baseline cortical VEP recordings were available for 14 patients (77.7%). No association was found between preoperative VF status and baseline presence of cortical VEPs (p = 0.27). Five of the 14 patients (35.7%) who underwent subcortical stimulation of the OR reported seeing phosphenes in the corresponding contralateral VF. There was a positive correlation (r = 0.899, p = 0.04) between the subcortical threshold stimulation intensity (3-11.5 mA) and the distance from the OR. Subcortical recordings from the OR demonstrated a typical VEP waveform in 10 of the 13 evaluated patients (76.9%). These waveforms were present only when recordings were obtained within 10 mm of the OR (p = 0.04). Seven patients (38.9%) had postoperative VF deterioration, and it was associated with a length of < 8 mm between the tumor and the OR (p = 0.05). CONCLUSIONS Intraoperative electrophysiological monitoring of the visual pathways is feasible but may be of limited value in preserving the functional integrity of the posterior visual pathways. Subcortical stimulation of the OR may identify the location of the OR when done in proximity to the pathways, but such proximity may be associated with increased risk of postoperative worsening of the VF deficit.

Quantifying the effect of colorization enhancement on mammogram images

NASA Astrophysics Data System (ADS)

Wojnicki, Paul J.; Uyeda, Elizabeth; Micheli-Tzanakou, Evangelia

2002-04-01

Current methods of radiological displays provide only grayscale images of mammograms. The limitation of the image space to grayscale provides only luminance differences and textures as cues for object recognition within the image. However, color can be an important and significant cue in the detection of shapes and objects. Increasing detection ability allows the radiologist to interpret the images in more detail, improving object recognition and diagnostic accuracy. Color detection experiments using our stimulus system, have demonstrated that an observer can only detect an average of 140 levels of grayscale. An optimally colorized image can allow a user to distinguish 250 - 1000 different levels, hence increasing potential image feature detection by 2-7 times. By implementing a colorization map, which follows the luminance map of the original grayscale images, the luminance profile is preserved and color is isolated as the enhancement mechanism. The effect of this enhancement mechanism on the shape, frequency composition and statistical characteristics of the Visual Evoked Potential (VEP) are analyzed and presented. Thus, the effectiveness of the image colorization is measured quantitatively using the Visual Evoked Potential (VEP).

Evoked potentials recorded during routine EEG predict outcome after perinatal asphyxia.

PubMed

Nevalainen, Päivi; Marchi, Viviana; Metsäranta, Marjo; Lönnqvist, Tuula; Toiviainen-Salo, Sanna; Vanhatalo, Sampsa; Lauronen, Leena

2017-07-01

To evaluate the added value of somatosensory (SEPs) and visual evoked potentials (VEPs) recorded simultaneously with routine EEG in early outcome prediction of newborns with hypoxic-ischemic encephalopathy under modern intensive care. We simultaneously recorded multichannel EEG, median nerve SEPs, and flash VEPs during the first few postnatal days in 50 term newborns with hypoxic-ischemic encephalopathy. EEG background was scored into five grades and the worst two grades were considered to indicate poor cerebral recovery. Evoked potentials were classified as absent or present. Clinical outcome was determined from the medical records at a median age of 21months. Unfavorable outcome included cerebral palsy, severe mental retardation, severe epilepsy, or death. The accuracy of outcome prediction was 98% with SEPs compared to 90% with EEG. EEG alone always predicted unfavorable outcome when it was inactive (n=9), and favorable outcome when it was normal or only mildly abnormal (n=17). However, newborns with moderate or severe EEG background abnormality could have either favorable or unfavorable outcome, which was correctly predicted by SEP in all but one newborn (accuracy in this subgroup 96%). Absent VEPs were always associated with an inactive EEG, and an unfavorable outcome. However, presence of VEPs did not guarantee a favorable outcome. SEPs accurately predict clinical outcomes in newborns with hypoxic-ischemic encephalopathy and improve the EEG-based prediction particularly in those newborns with severely or moderately abnormal EEG findings. SEPs should be added to routine EEG recordings for early bedside assessment of newborns with hypoxic-ischemic encephalopathy. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Multimodal evoked potentials in patients with multiple sclerosis in assessment of the course of the disease.

PubMed

Łabuz-Roszak, Beata; Torbus, Magdalena; Kubicka-Bączyk, Katarzyna; Machowska-Majchrzak, Agnieszka; Kierber, Agata; Borucka, Katarzyna; Zellner, Małgorzata; Starostak-Tatar, Anna; Pierzchała, Krystyna

Multiple sclerosis (MS) is a chronic inflammatory, demyelinating disease of the central nervous system with a multifocal damage. The assessment of the MS course by multimodal evoked potentials (EP). We evaluated 95 patients (63 female, 32 male) with relapsing-remitting MS in the average age of 36.4±10.4. The average disease duration was 4.6±7.4 year. Among them, 48 patients (50.5%) were treated with immunomodulatory drugs. All patients underwent neurological examination and EP testing: VEP (visual evoked potentials), SEP (somatosensory evoked potentials), endogenous potential P300. The latencies of following waves were evaluated: P100 (VEP), N4 , N9 , N13, N20, P22 (SEP) and P300, with the reference values of the Neurophysiological Research Laboratory of the Department of Neurology in Zabrze. Abnormal VEP(I) was found in 80 patients (84.2%), SEP(I) in 9 patients (9.5%), P300(I) in 15 patients (15.8%). Abnormal result of the control research VEP (II) was found in 23 patients (82.1%), SEP(II) in 1 patient (3.6%), P300(II) in 4 patients (14.3%). The average values of the waves latencies in the control study were higher, however the statistical significance was not found. The correlation was observed between EDSS, and N20 and P22. No relationship was found between EP and age, disease duration, number of relapses and treatment. In the era of neuroimaging, usage of EP in the diagnosis and assessment of MS is limited. Electrophysiological studies may be used in addition to the clinical examination to confirm the multifocal damage.

[Effects of sevoflurane and propofol on evoked potentials during neurosurgical anesthesia].

PubMed

Nakagawa, Itsuo; Hidaka, Syozo; Okada, Hironori; Kubo, Takashi; Okamura, Kenta; Kato, Takahiro

2006-06-01

The effect of anesthetics on somatosensory evoked potential (SEP) and auditory brain stem response (ABR) has been a subject of intense reseach over the last two decades. In fact, volatile anesthetics have been repeatedly shown to decrease cortical amplitude in a dose-dependent fashion but the information regarding the effect of propofol is incomplete. The purpose of this study was to compare the effects of sevoflurane and propofol on evoked potentials during comparable depth of anesthesia guided by bispectral index (BIS). Forty four patients scheduled for neurosurgery were studied. Anesthesia was maintained with intravenous propofol using target controlled infusion (TCI). We measured the change of amplitude and latency of SEP(N20-P25), ABR (V wave) and visual evoked potential (VEP: P100) at three sets of sevoflurane (0%, 1%, 2%) or propofol concentrations (effect site concentration of 1.5, 2.0, 3.0 microug x ml(-1)). BIS monitor was used to measure relative depth of hypnosis. With increasing concentrations of sevoflurane (0, 1% and 2%), SEP showed dose-related reduction in its amplitude, ABR produced less marked changes and VEP showed a significant reduction at 1%. VEP at the propofol concentration of 3.0 microg x ml(-1) was decreased significantly compared with the amplitude at 1.5 microg x ml(-1) concentration. No significant change was observed with SEP and ABR during the change of propofol dosages. BIS values were almost the same with each anesthetics. VEP was most strongly affected with anesthetics, and ABR showed less marked influence of sevoflurane and propofol. Propofol based TIVA technique would induce less change in evoked potentials than sevoflurane.

Discrepancy between structural and functional visual recovery in patients after trans-sphenoidal pituitary adenoma resection.

PubMed

Qiao, Nidan; Ye, Zhao; Shou, Xuefei; Wang, Yongfei; Li, Shiqi; Wang, Min; Zhao, Yao

2016-12-01

The relationship between functional and structural measurements is of fundamental importance in monitoring treatment and progression in patients with pituitary adenoma. In the present study, we examined the association between longitudinal changes in standard automated perimetry (SAP), retinal nerve fiber layer (RNFL) thickness and multifocal visual evoked potential (mfVEP) amplitude after transsphenoidal surgery. Thirty patients with pituitary adenoma were recruited from Huashan Hospital between September 2010 and January 2014. The examination included pupil examination, anterior and posterior segment examination, SAP, RNFL and mfVEP. At three months and nine months after transsphenoid surgery, follow-up measurements were conducted in twenty-three patients, and at 18 months after surgery, the same examinations were performed in seven patients. The average age of patients was 42.6±12.1years, with 23 males and 7 females. The mean score of SAP improved significantly: 1.75 before surgery; 0.62 at three months after surgery (p=0.00) and 0.50 at nine months after surgery (p=0.00). No significant improvement in RNFL thickness was observed at three months or nine months after surgery. The mean score of mfVEP also improved significantly: 0.85 before surgery; 0.53 at three months (p=0.00) and 0.38 at nine months after surgery (P=0.00). No statistical difference was observed in the outcome of patients at nine months of follow-up and 18 months of follow-up. Visual field and mfVEP recovery with unchanged RNFL thickness was observed in patients after transsphenoid pituitary adenoma resection. Copyright © 2016. Published by Elsevier B.V.

A comparative study of the usefulness of color vision, photostress recovery time, and visual evoked potential tests in early detection of ocular toxicity from hydroxychloroquine.

PubMed

Heravian, Javad; Saghafi, Massoud; Shoeibi, Naser; Hassanzadeh, Samira; Shakeri, Mohammad Taghi; Sharepoor, Maria

2011-08-01

Ocular toxicity from hydroxychloroquine (HCQ) is rare, but its potential permanence and severity makes it imperative to employ measures and screening protocols to minimize its occurrence. This study was performed to assess the usefulness of color vision, photo stress recovery time (PSRT), and visual evoked potentials (VEP) in early detection of ocular toxicity of HCQ, in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). 86 patients were included in the study and divided into three groups: (1) with history of HCQ use: interventional 1 (Int.1) without fundoscopic changes and Int.2 with fundoscopic changes; and (2) without history of HCQ use, as control. Visual field, color vision, PSRT and VEP results were recorded for all patients and the effect of age, disease duration, treatment duration and cumulative dose of HCQ on each test was assessed in each group. There was a significant relationship among PSRT and age, treatment duration, cumulative dose of HCQ and disease duration (P<0.001 for all). Color vision was normal in all the cases. P100 amplitude was not different between the three groups (P=0.846), but P100 latency was significantly different (P=0.025) and for Int.2 it was greater than the others. The percentage of abnormal visual fields for Int.2 was more than Int.1 and control groups (P=0.002 and P=0.005 respectively), but Int.1 and control groups were not significantly different (P>0.50). In the early stages of maculopathy, P100 latencies of VEP and PSRT are useful predictors of HCQ ocular toxicity. In patients without ocular symptoms and fundoscopic changes, the P100 latency of VEP predicts more precisely than the others.

Large Amplitude Cortical Evoked Potentials in Nonepileptic Patients. Reviving an Old Neurophysiologic Tool to Help Detect CNS Pathology.

PubMed

Martín-Palomeque, Guillermo; Castro-Ortiz, Antonio; Pamplona-Valenzuela, Pilar; Saiz-Sepúlveda, Miguel Á; Cabañes-Martínez, Lidia; López, Jaime R

2017-01-01

Although large amplitude evoked potentials (EPs) are typically associated with progressive myoclonic epilepsy patients, giant EPs imply central nervous system (CNS) hyperexcitability and can be seen in various nonepileptic disorders. We performed a retrospective chart review including history, physical examination, imaging and diagnostic studies of nonepileptic patients with large amplitude somatosensory evoked potentials (SSEPs) and visual evoked potentials (VEPs) during 2007 to 2013. Large amplitude EPs were defined as follows: VEPs (N75-P100) >18 μV; and SSEPs (N20-P25) >6.4 μV. Recording montage for VEPs was Oz-Cz and SSEPs C3'/C4'-Fz. Fifty-two patients (33 females, 19 males; age range, 9-90 years) were identified. No CNS pathology was detected in 7 patients. All remaining patients were diagnosed with new CNS disorders including: vascular (37%); myelopathies (13%); demyelinating (11%); space occupying lesions (8.7%); syringomyelia (8.7%); hydrocephalus (6.5%); Vitamin B-12 deficiency (4.3%); multiple system atrophy (4.3%); and toxins (2.2%). This study supports the notion that large amplitude EP implies CNS hyperexcitability and CNS disease. These results confirm the utility of EP studies in patients with suspected CNS pathology.

Social vision: sustained perceptual enhancement of affective facial cues in social anxiety

PubMed Central

McTeague, Lisa M.; Shumen, Joshua R.; Wieser, Matthias J.; Lang, Peter J.; Keil, Andreas

2010-01-01

Heightened perception of facial cues is at the core of many theories of social behavior and its disorders. In the present study, we continuously measured electrocortical dynamics in human visual cortex, as evoked by happy, neutral, fearful, and angry faces. Thirty-seven participants endorsing high versus low generalized social anxiety (upper and lower tertiles of 2,104 screened undergraduates) viewed naturalistic faces flickering at 17.5 Hz to evoke steady-state visual evoked potentials (ssVEPs), recorded from 129 scalp electrodes. Electrophysiological data were evaluated in the time-frequency domain after linear source space projection using the minimum norm method. Source estimation indicated an early visual cortical origin of the face-evoked ssVEP, which showed sustained amplitude enhancement for emotional expressions specifically in individuals with pervasive social anxiety. Participants in the low symptom group showed no such sensitivity, and a correlational analysis across the entire sample revealed a strong relationship between self-reported interpersonal anxiety/avoidance and enhanced visual cortical response amplitude for emotional, versus neutral expressions. This pattern was maintained across the 3500 ms viewing epoch, suggesting that temporally sustained, heightened perceptual bias towards affective facial cues is associated with generalized social anxiety. PMID:20832490

Subadditive responses to extremely short blue and green pulsed light on visual evoked potentials, pupillary constriction and electroretinograms.

PubMed

Lee, Soomin; Uchiyama, Yuria; Shimomura, Yoshihiro; Katsuura, Tetsuo

2017-11-17

The simultaneous exposure to blue and green light was reported to result in less melatonin suppression than monochromatic exposure to blue or green light. Here, we conducted an experiment using extremely short blue- and green-pulsed light to examine their visual and nonvisual effects on visual evoked potentials (VEPs), pupillary constriction, electroretinograms (ERGs), and subjective evaluations. Twelve adult male subjects were exposed to three light conditions: blue-pulsed light (2.5-ms pulse width), green-pulsed light (2.5-ms pulse width), and simultaneous blue- and green-pulsed light with white background light. We measured the subject's pupil diameter three times in each condition. Then, after 10 min of rest, the subject was exposed to the same three light conditions. We measured the averaged ERG and VEP during 210 pulsed-light exposures in each condition. We also determined subjective evaluations using a visual analog scale (VAS) method. The pupillary constriction during the simultaneous exposure to blue- and green-pulsed light was significantly lower than that during the blue-pulsed light exposure despite the double irradiance intensity of the combination. We also found that the b/|a| wave of the ERGs during the simultaneous exposure to blue- and green-pulsed light was lower than that during the blue-pulsed light exposure. We confirmed the subadditive response to pulsed light on pupillary constriction and ERG. However, the P100 of the VEPs during the blue-pulsed light were smaller than those during the simultaneous blue- and green-pulsed light and green-pulsed light, indicating that the P100 amplitude might depend on the luminance of light. Our findings demonstrated the effect of the subadditive response to extremely short pulsed light on pupillary constriction and ERG responses. The effects on ipRGCs by the blue-pulsed light exposure are apparently reduced by the simultaneous irradiation of green light. The blue versus yellow (b/y) bipolar cells in the retina might be responsible for this phenomenon.

A fast visual evoked potential method for functional assessment and follow-up of childhood optic gliomas.

PubMed

Trisciuzzi, Maria Teresa S; Riccardi, Riccardo; Piccardi, Marco; Iarossi, Giancarlo; Buzzonetti, Luca; Dickmann, Anna; Colosimo, Cesare; Ruggiero, Antonio; Di Rocco, Concezio; Falsini, Benedetto

2004-01-01

To evaluate a fast technique of visual evoked potentials (VEPs) recording, in response to steady-state luminance stimuli (SS-LVEPs), for functional assessment and follow-up of childhood optic gliomas (OGs). Eighteen OG patients (age range: 3.5-18 years), with different degrees of optic pathway damage severity, were examined. Sixteen age-matched normal subjects served as controls. Ten of the 18 OG patients were re-tested 1-3 months after the first examination. SS-LVEPs were elicited by a sinusoidally-modulated flickering (8 Hz) uniform field, generated by a light emitting diode (LED)-array and presented monocularly in a mini-ganzfeld. Amplitude and phase of the Fourier-analyzed response fundamental (1F) and second harmonic (2F) were measured. The full VEP protocol had a median duration of 6 min (range: 4-12). When compared to normal control values, median 1F and 2F SS-LVEP amplitudes of OG patients were reduced (P<0.01), with a borderline increase in 2F phase lag (P<0.05). In 11 OG patients with asymmetric optic pathway damage in between-eye comparisons, median 1F amplitude losses were greater (P<0.01) in fellow eyes with more severe damage. No significant interocular difference was observed in control subjects. Median test-retest changes of 1F and 2F component were <20% and 30 degrees for amplitude and phase, respectively. In individual OG patients, 1F and 2F amplitudes were positively correlated (P<0.01) with visual acuity. 1F amplitude losses were correlated (P=0.01) with the severity of optic disc atrophy. Considering both 1F and 2F abnormalities, diagnostic sensitivity of SS-LVEP in detecting OG-induced optic pathways damage was 83.3%. The present findings support the use of this technique, as an alternative to pattern VEPs, for functional assessment and follow-up of OG in uncooperative children.

Control of humanoid robot via motion-onset visual evoked potentials

PubMed Central

Li, Wei; Li, Mengfan; Zhao, Jing

2015-01-01

This paper investigates controlling humanoid robot behavior via motion-onset specific N200 potentials. In this study, N200 potentials are induced by moving a blue bar through robot images intuitively representing robot behaviors to be controlled with mind. We present the individual impact of each subject on N200 potentials and discuss how to deal with individuality to obtain a high accuracy. The study results document the off-line average accuracy of 93% for hitting targets across over five subjects, so we use this major component of the motion-onset visual evoked potential (mVEP) to code people's mental activities and to perform two types of on-line operation tasks: navigating a humanoid robot in an office environment with an obstacle and picking-up an object. We discuss the factors that affect the on-line control success rate and the total time for completing an on-line operation task. PMID:25620918

Delayed visual maturation in infants: a disorder of figure-ground separation?

PubMed

Harris, C M; Kriss, A; Shawkat, F; Taylor, D; Russell-Eggitt, I

1996-01-01

Delayed visual maturation (DVM) is characterised by visual unresponsiveness in early infancy, which subsequently improves spontaneously to normal levels. We studied the optokinetic response and recorded pattern reversal VEPs in six infants with DVM (aged 2-4 months) when they were at the stage of complete visual unresponsiveness. Although no saccades or visual tracking with the eyes or head could be elicited to visual objects, a normal full-field rapid buildup OKN response occurred when viewing biocularly or during monocular stimulation in the temporo-nasal direction of the viewing eye. Almost no monocular OKN could be elicited in the naso-temporal direction, which was significantly poorer than normal age-matched infants. No OKN quick phases were missed, and there were no other signs of "ocular motor apraxia." VEPs were normal in amplitude and latency for age. It appears, therefore, that infants with DVM are delayed in orienting to local regions of the visual field, but can respond to full-field motion. The presence of normal OKN quick-phases and slow-phases suggests normal brain stem function, and the presence of normal pattern VEPs suggests a normal retino-geniculo-striate pathway. These oculomotor and electrophysiological findings suggest delayed development of extra-striate cortical structures, possibly involving either an abnormality in figure-ground segregation or in attentional pathways.

Postnatal development of EEG patterns, catecholamine contents and myelination, and effect of hyperthyroidism in Suncus brain.

PubMed

Takeuchi, T; Sitizyo, K; Harada, E

1998-03-01

The postnatal development of the central nervous system (CNS) in house musk shrew in the early stage of maturation was studied. The electroencephalogram (EEG) and visual evoked potential (VEP) in association with catecholamine contents and myelin basic protein (MBP) immunoreactivity were carried out from the 1st to the 20th day of postnatal age. Different EEG patterns which were specific to behavioral states (awake and drowsy) were first recorded on the 5th day, and the total power which was obtained by power spectrum analysis increased after this stage. The latencies of all peaks in VEP markedly shortened between the 5th and the 7th day. Noradrenalin (NA) content of the brain showed a slight increase after the 3rd day, and reached maximum levels on the 7th day, which was delayed a few days compared to dopamine (DA). In hyperthyroidism, the peak latency of VEP was shortened and biosynthesis of NA in cerebral cortex and DA in hippocampus was accelerated. The most obvious change in MBP-immunoreactivity of the telencephalon occurred from the 7th to the 10th day. These morphological changes in the brain advanced at the identical time-course to those in the electrophysiological development and increment of DA and NA contents.

Additive effects of emotional content and spatial selective attention on electrocortical facilitation.

PubMed

Keil, Andreas; Moratti, Stephan; Sabatinelli, Dean; Bradley, Margaret M; Lang, Peter J

2005-08-01

Affectively arousing visual stimuli have been suggested to automatically attract attentional resources in order to optimize sensory processing. The present study crosses the factors of spatial selective attention and affective content, and examines the relationship between instructed (spatial) and automatic attention to affective stimuli. In addition to response times and error rate, electroencephalographic data from 129 electrodes were recorded during a covert spatial attention task. This task required silent counting of random-dot targets embedded in a 10 Hz flicker of colored pictures presented to both hemifields. Steady-state visual evoked potentials (ssVEPs) were obtained to determine amplitude and phase of electrocortical responses to pictures. An increase of ssVEP amplitude was observed as an additive function of spatial attention and emotional content. Statistical parametric mapping of this effect indicated occipito-temporal and parietal cortex activation contralateral to the attended visual hemifield in ssVEP amplitude modulation. This difference was most pronounced during selection of the left visual hemifield, at right temporal electrodes. In line with this finding, phase information revealed accelerated processing of aversive arousing, compared to affectively neutral pictures. The data suggest that affective stimulus properties modulate the spatiotemporal process along the ventral stream, encompassing amplitude amplification and timing changes of posterior and temporal cortex.

Neuro-ophthalmologic evaluation, quality of life, and functional disability in patients with MS.

PubMed

Garcia-Martin, Elena; Rodriguez-Mena, Diego; Herrero, Raquel; Almarcegui, Carmen; Dolz, Isabel; Martin, Jesus; Ara, Jose R; Larrosa, Jose M; Polo, Vicente; Fernández, Javier; Pablo, Luis E

2013-07-02

To evaluate correlations between longitudinal changes in neuro-ophthalmologic measures and quality of life (QOL) and disability in patients with multiple sclerosis (MS), using optical coherence tomography (OCT), visual evoked potentials (VEP), and visual field examination. Fifty-four patients with relapsing-remitting MS were enrolled in this study and underwent Multiple Sclerosis Quality of Life questionnaire (54 items) (MSQOL-54) and Expanded Disability Status Scale (EDSS) evaluation, as well as complete neuro-ophthalmologic examination including visual field testing and retinal nerve fiber layer (RNFL) measurements using Cirrus and Spectralis OCT and VEP. All patients were re-evaluated at 12, 24, and 36 months. Logistical regression was performed to analyze which measures, if any, could predict QOL. Overall, RNFL thickness results at the baseline evaluation were significantly different from those at 3 years (p ≤ 0.05), but there were no differences in functional measures (visual acuity, contrast sensitivity, color vision, visual field, and VEP). A reduced MSQOL-54 score was associated with an increase in EDSS score and a decrease in both functional and structural parameters. Patients with longer MS duration presented with a lower MSQOL-54 score (reduction in QOL). Patients with progressive axonal loss as seen in RNFL results had a lower QOL and more functional disability.

L-/M-cone opponency in visual evoked potentials of human cortex.

PubMed

Barboni, Mirella Telles Salgueiro; Nagy, Balázs Vince; Martins, Cristiane Maria Gomes; Bonci, Daniela Maria Oliveria; Hauzman, Einat; Aher, Avinash; Tsai, Tina I; Kremers, Jan; Ventura, Dora Fix

2017-08-01

L and M cones send their signals to the cortex using two chromatic (parvocellular and blue-yellow koniocellular) and one luminance (magnocellular) pathways. These pathways contain ON and OFF subpathways that respond to excitation increments and decrements respectively. Here, we report on visually evoked potentials (VEP) recordings that reflect L- and M-cone driven increment (LI and MI) and decrement (LD and MD) activity. VEP recordings were performed on 12 trichromats and four dichromats (two protanopes and two deuteranopes). We found that the responses to LI strongly resembled those to MD, and that LD and MI responses were very similar. Moreover, the lack of a photoreceptor type (L or M) in the dichromats led to a dominance of the ON pathway of the remaining photoreceptor type. These results provide electrophysiological evidence that antagonistic L/M signal processing, already present in the retina and the lateral geniculate nucleus (LGN), is also observed at the visual cortex. These data are in agreement with results from human psychophysics where MI stimuli lead to a perceived brightness decrease whereas LI stimuli resulted in perceived brightness increases. VEP recording is a noninvasive tool that can be easily and painlessly applied. We propose that the technique may provide information in the diagnosis of color vision deficiencies.

Effects of maternal inhalation of gasoline evaporative ...

EPA Pesticide Factsheets

In order to assess potential health effects resulting from exposure to ethanol-gasoline blend vapors, we previously conducted neurophysiological assessment of sensory function following gestational exposure to 100% ethanol vapor (Herr et al., Toxicologist, 2012). For comparison purposes, the current study investigated the same measures after gestational exposure to 100% gasoline evaporative condensates (GVC). Pregnant Long-Evans rats were exposed to 0, 3K, 6K, or 9K ppm GVC vapors for 6.5 h/day over GD9 – GD20. Sensory evaluations of male offspring began around PND106. Peripheral nerve function (compound action potentials, NCV), somatosensory (cortical and cerebellar evoked potentials), auditory (brainstem auditory evoked responses), and visual evoked responses were assessed. Visual function assessment included pattern elicited visual evoked potentials (VEP), VEP contrast sensitivity, and electroretinograms (ERG) recorded from dark-adapted (scotopic) and light-adapted (photopic) flashes, and UV and green flicker. Although some minor statistical differences were indicated for auditory and somatosensory responses, these changes were not consistently dose- or stimulus intensity-related. Scotopic ERGs had a statistically significant dose-related decrease in the b-wave implicit time. All other parameters of ERGs and VEPs were unaffected by treatment. All physiological responses showed changes related to stimulus intensity, and provided an estimate of detectable le

The effect of ingested sulfite on visual evoked potentials, lipid peroxidation, and antioxidant status of brain in normal and sulfite oxidase-deficient aged rats.

PubMed

Ozsoy, Ozlem; Aras, Sinem; Ozkan, Ayse; Parlak, Hande; Aslan, Mutay; Yargicoglu, Piraye; Agar, Aysel

2016-07-01

Sulfite, commonly used as a preservative in foods, beverages, and pharmaceuticals, is a very reactive and potentially toxic molecule which is detoxified by sulfite oxidase (SOX). Changes induced by aging may be exacerbated by exogenous chemicals like sulfite. The aim of this study was to investigate the effects of ingested sulfite on visual evoked potentials (VEPs) and brain antioxidant statuses by measuring superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities. Brain lipid oxidation status was also determined via thiobarbituric acid reactive substances (TBARS) in normal- and SOX-deficient aged rats. Rats do not mimic the sulfite responses seen in humans because of their relatively high SOX activity level. Therefore this study used SOX-deficient rats since they are more appropriate models for studying sulfite toxicity. Forty male Wistar rats aged 24 months were randomly assigned to four groups: control (C), sulfite (S), SOX-deficient (D) and SOX-deficient + sulfite (DS). SOX deficiency was established by feeding rats with low molybdenum (Mo) diet and adding 200 ppm tungsten (W) to their drinking water. Sulfite in the form of sodium metabisulfite (25 mg kg(-1) day(-1)) was given by gavage. Treatment continued for 6 weeks. At the end of the experimental period, flash VEPs were recorded. Hepatic SOX activity was measured to confirm SOX deficiency. SOX-deficient rats had an approximately 10-fold decrease in hepatic SOX activity compared with the normal rats. The activity of SOX in deficient rats was thus in the range of humans. There was no significant difference between control and treated groups in either latence or amplitude of VEP components. Brain SOD, CAT, and GPx activities and brain TBARS levels were similar in all experimental groups compared with the control group. Our results indicate that exogenous administration of sulfite does not affect VEP components and the antioxidant/oxidant status of aged rat brains. © The Author(s) 2014.

Cross-Modal and Intra-Modal Characteristics of Visual Function and Speech Perception Performance in Postlingually Deafened, Cochlear Implant Users

PubMed Central

Kim, Min-Beom; Shim, Hyun-Yong; Jin, Sun Hwa; Kang, Soojin; Woo, Jihwan; Han, Jong Chul; Lee, Ji Young; Kim, Martha; Cho, Yang-Sun

2016-01-01

Evidence of visual-auditory cross-modal plasticity in deaf individuals has been widely reported. Superior visual abilities of deaf individuals have been shown to result in enhanced reactivity to visual events and/or enhanced peripheral spatial attention. The goal of this study was to investigate the association between visual-auditory cross-modal plasticity and speech perception in post-lingually deafened, adult cochlear implant (CI) users. Post-lingually deafened adults with CIs (N = 14) and a group of normal hearing, adult controls (N = 12) participated in this study. The CI participants were divided into a good performer group (good CI, N = 7) and a poor performer group (poor CI, N = 7) based on word recognition scores. Visual evoked potentials (VEP) were recorded from the temporal and occipital cortex to assess reactivity. Visual field (VF) testing was used to assess spatial attention and Goldmann perimetry measures were analyzed to identify differences across groups in the VF. The association of the amplitude of the P1 VEP response over the right temporal or occipital cortex among three groups (control, good CI, poor CI) was analyzed. In addition, the association between VF by different stimuli and word perception score was evaluated. The P1 VEP amplitude recorded from the right temporal cortex was larger in the group of poorly performing CI users than the group of good performers. The P1 amplitude recorded from electrodes near the occipital cortex was smaller for the poor performing group. P1 VEP amplitude in right temporal lobe was negatively correlated with speech perception outcomes for the CI participants (r = -0.736, P = 0.003). However, P1 VEP amplitude measures recorded from near the occipital cortex had a positive correlation with speech perception outcome in the CI participants (r = 0.775, P = 0.001). In VF analysis, CI users showed narrowed central VF (VF to low intensity stimuli). However, their far peripheral VF (VF to high intensity stimuli) was not different from the controls. In addition, the extent of their central VF was positively correlated with speech perception outcome (r = 0.669, P = 0.009). Persistent visual activation in right temporal cortex even after CI causes negative effect on outcome in post-lingual deaf adults. We interpret these results to suggest that insufficient intra-modal (visual) compensation by the occipital cortex may cause negative effects on outcome. Based on our results, it appears that a narrowed central VF could help identify CI users with poor outcomes with their device. PMID:26848755

[Multifocal visual electrophysiology in visual function evaluation].

PubMed

Peng, Shu-Ya; Chen, Jie-Min; Liu, Rui-Jue; Zhou, Shu; Liu, Dong-Mei; Xia, Wen-Tao

2013-08-01

Multifocal visual electrophysiology, consisting of multifocal electroretinography (mfERG) and multifocal visual evoked potential (mfVEP), can objectively evaluate retina function and retina-cortical conduction pathway status by stimulating many local retinal regions and obtaining each local response simultaneously. Having many advantages such as short testing time and high sensitivity, it has been widely used in clinical ophthalmology, especially in the diagnosis of retinal disease and glaucoma. It is a new objective technique in clinical forensic medicine involving visual function evaluation of ocular trauma in particular. This article summarizes the way of stimulation, the position of electrodes, the way of analysis, the visual function evaluation of mfERG and mfVEP, and discussed the value of multifocal visual electrophysiology in forensic medicine.

Combining near-infrared spectroscopy with electroencephalography and repetitive transcranial magnetic stimulation

NASA Astrophysics Data System (ADS)

Näsi, Tiina; Kotilahti, Kalle; Mäki, Hanna; Nissilä, Ilkka; Meriläinen, Pekka

2009-07-01

The objective of the study was to assess the usability of a near-infrared spectroscopy (NIRS) device in multimodal measurements. We combined NIRS with electroencephalography (EEG) to record hemodynamic responses and evoked potentials simultaneously, and with transcranial magnetic stimulation (TMS) to investigate hemodynamic responses to repetitive TMS (rTMS). Hemodynamic responses and visual evoked potentials (VEPs) to 3, 6, and 12 s stimuli consisting of pattern-reversing checkerboards were successfully recorded in the NIRS/EEG measurement, and ipsi- and contralateral hemodynamic responses to 0.5, 1, and 2 Hz rTMS in the NIRS/TMS measurement. In the NIRS/EEG measurements, the amplitudes of the hemodynamic responses increased from 3- to 6-s stimulus, but not from 6- to 12-s stimulus, and the VEPs showed peaks N75, P100, and N135. In the NIRS/TMS measurements, the 2-Hz stimulus produced the strongest hemodynamic responses compared to the 0.5- and 1-Hz stimuli. In two subjects oxyhemoglobin concentration decreased and in one increased as a consequence of the 2-Hz rTMS. To locate the origin of the measured NIRS responses, methods have to be developed to investigate TMS-induced scalp muscle contractions. In the future, multimodal measurements may prove useful in monitoring or treating diseases such as stroke or Alzheimer's disease.

Defective chromatic and achromatic visual pathways in developmental dyslexia: Cues for an integrated intervention programme.

PubMed

Bonfiglio, Luca; Bocci, Tommaso; Minichilli, Fabrizio; Crecchi, Alessandra; Barloscio, Davide; Spina, Donata Maria; Rossi, Bruno; Sartucci, Ferdinando

2017-01-01

As well as obtaining confirmation of the magnocellular system involvement in developmental dyslexia (DD); the aim was primarily to search for a possible involvement of the parvocellular system; and, furthermore, to complete the assessment of the visual chromatic axis by also analysing the koniocellular system. Visual evoked potentials (VEPs) in response to achromatic stimuli with low luminance contrast and low spatial frequency, and isoluminant red/green and blue/yellow stimuli with high spatial frequency were recorded in 10 dyslexic children and 10 age- and sex-matched, healthy subjects. Dyslexic children showed delayed VEPs to both achromatic stimuli (magnocellular-dorsal stream) and isoluminant red/green and blue/yellow stimuli (parvocellular-ventral and koniocellular streams). To our knowledge, this is the first time that a dysfunction of colour vision has been brought to light in an objective way (i.e., by means of electrophysiological methods) in children with DD. These results give rise to speculation concerning the need for a putative approach for promoting both learning how to read and/or improving existing reading skills of children with or at risk of DD. The working hypothesis would be to combine two integrated interventions in a single programme aimed at fostering the function of both the magnocellular and the parvocellular streams.

Tagging cortical networks in emotion: a topographical analysis

PubMed Central

Keil, Andreas; Costa, Vincent; Smith, J. Carson; Sabatinelli, Dean; McGinnis, E. Menton; Bradley, Margaret M.; Lang, Peter J.

2013-01-01

Viewing emotional pictures is associated with heightened perception and attention, indexed by a relative increase in visual cortical activity. Visual cortical modulation by emotion is hypothesized to reflect re-entrant connectivity originating in higher-order cortical and/or limbic structures. The present study used dense-array electroencephalography and individual brain anatomy to investigate functional coupling between the visual cortex and other cortical areas during affective picture viewing. Participants viewed pleasant, neutral, and unpleasant pictures that flickered at a rate of 10 Hz to evoke steady-state visual evoked potentials (ssVEPs) in the EEG. The spectral power of ssVEPs was quantified using Fourier transform, and cortical sources were estimated using beamformer spatial filters based on individual structural magnetic resonance images. In addition to lower-tier visual cortex, a network of occipito-temporal and parietal (bilateral precuneus, inferior parietal lobules) structures showed enhanced ssVEP power when participants viewed emotional (either pleasant or unpleasant), compared to neutral pictures. Functional coupling during emotional processing was enhanced between the bilateral occipital poles and a network of temporal (left middle/inferior temporal gyrus), parietal (bilateral parietal lobules), and frontal (left middle/inferior frontal gyrus) structures. These results converge with findings from hemodynamic analyses of emotional picture viewing and suggest that viewing emotionally engaging stimuli is associated with the formation of functional links between visual cortex and the cortical regions underlying attention modulation and preparation for action. PMID:21954087

Experience-enabled enhancement of adult visual cortex function.

PubMed

Tschetter, Wayne W; Alam, Nazia M; Yee, Christopher W; Gorz, Mario; Douglas, Robert M; Sagdullaev, Botir; Prusky, Glen T

2013-03-20

We previously reported in adult mice that visuomotor experience during monocular deprivation (MD) augmented enhancement of visual-cortex-dependent behavior through the non-deprived eye (NDE) during deprivation, and enabled enhanced function to persist after MD. We investigated the physiological substrates of this experience-enabled form of adult cortical plasticity by measuring visual behavior and visually evoked potentials (VEPs) in binocular visual cortex of the same mice before, during, and after MD. MD on its own potentiated VEPs contralateral to the NDE during MD and shifted ocular dominance (OD) in favor of the NDE in both hemispheres. Whereas we expected visuomotor experience during MD to augment these effects, instead enhanced responses contralateral to the NDE, and the OD shift ipsilateral to the NDE were attenuated. However, in the same animals, we measured NMDA receptor-dependent VEP potentiation ipsilateral to the NDE during MD, which persisted after MD. The results indicate that visuomotor experience during adult MD leads to enduring enhancement of behavioral function, not simply by amplifying MD-induced changes in cortical OD, but through an independent process of increasing NDE drive in ipsilateral visual cortex. Because the plasticity is resident in the mature visual cortex and selectively effects gain of visual behavior through experiential means, it may have the therapeutic potential to target and non-invasively treat eye- or visual-field-specific cortical impairment.

Simple and powerful visual stimulus generator.

PubMed

Kremlácek, J; Kuba, M; Kubová, Z; Vít, F

1999-02-01

We describe a cheap, simple, portable and efficient approach to visual stimulation for neurophysiology which does not need any special hardware equipment. The method based on an animation technique uses the FLI autodesk animator format. This form of the animation is replayed by a special program ('player') providing synchronisation pulses toward recording system via parallel port. The 'player is running on an IBM compatible personal computer under MS-DOS operation system and stimulus is displayed on a VGA computer monitor. Various stimuli created with this technique for visual evoked potentials (VEPs) are presented.

Subnormal visual acuity (SVAS) and albinism in Mexican 12-13-year-old children.

PubMed

Sjöström, A; Kraemer, M; Ohlsson, J; Garay-Cerro, G; Abrahamsson, M; Villarreal, G

2004-01-01

In a previous study the vision of 1046 12-13-year-olds in Sweden was examined. Of those 67 had some kind of visual disturbances and in 20 no obvious cause was found. In this group, defined as children with subnormal visual acuity syndromes (SVAS), albinism was shown to be a major cause to the visual dysfunction giving a prevalence of about 1%. This is about 100 times higher than previous figures. Albinism can therefore be the cause in many cases of unexplained low visual acuity, at least in Sweden. Subnormal visual acuity is usually found in 2-4% in a pediatric population and is often called 'amblyopia'. The Swedish study showed that in many cases 'amblyopia' should be replaced by 'SVAS' and further investigation. The present Mexican study was designed identically to the Swedish study. The objective was to describe the distribution of visual acuity and the prevalence of ocular disorders, including incidence of subnormal visual acuity (SVAS) and the occurrence of albinism in a Mexican population of 12-13-year-olds. Altogether 1035 children, 12-13 years of age, were examined. A total number of 344 children were referred to the university pediatric eye clinic for further examination. 272 of these had simple refractive errors, 59 were diagnosed with an ophthalmological disorder and 13 children could not be pathologically classified. These were referred to a second ophthalmological examination, including VEP (Visual Evoked Potential) recordings. VEP reveals an asymmetric (right vs. left) cortical response after monocular stimulation in albinism. No child showed iris translucency or any other typical albinoic sign. VEP was recorded from 11 children. Three children showed an asymmetric VEP and were classified as albinos. The VEP response was normal in 8 of the children. The results indicate that albinism is common in Mexico, although not as common as in a similar Swedish population. A prevalence of albinism of approximately 0.3% was found in the Mexican population, compared to approximately 1% in the Swedish study group. The number of albinos was much higher in both study groups than to be expected from previous estimates. The difference between the Swedish and the Mexican figures may be explained by the general difference in pigmentation between Sweden and Mexico and thus probably by the subsequent lower number of commonly occurring albino foci in the Mexican heritage. It is emphasised that in investigations of children with SVAS, also in countries with a generally high pigmentation level, electro-physiological examinations are important, to be able to reveal albinism, but also to exclude or verify other conditions in the SVAS group, for example neurometabolic conditions.

Beta-zone parapapillary atrophy and multifocal visual evoked potentials in eyes with glaucomatous optic neuropathy.

PubMed

De Moraes, Carlos Gustavo; Ketner, Scott; Teng, Christopher C; Ehrlich, Joshua R; Raza, Ali S; Liebmann, Jeffrey M; Ritch, Robert; Hood, Donald C

2011-08-01

We investigated changes in multifocal visual evoked potential (mfVEP) responses due to beta-zone parapapillary atrophy (ßPPA). Patients with glaucomatous optic neuropathy (GON) with or without standard achromatic perimetry (SAP) abnormalities were referred for mfVEP testing during a 2-year period. Eyes with good quality optic disc stereophotographs and reliable SAP results were included. The mfVEP monocular mean latency delays (ms) and amplitudes (SNR) were analyzed. Age, SAP mean deviation (MD), pattern standard deviation (PSD), and spherical equivalent (SE) were analyzed in the multivariate model. Generalized estimated equations were used for comparisons between groups after adjusting for inter-eye associations. Of 394 eyes of 200 patients, 223 (57%) had ßPPA. The ßPPA eyes were older (59.6 ± 13.7 vs. 56.5 ± 13.7 year, P = 0.02), more myopic (-4.0 ± 3.5 vs. -1.3 ± 3.5 D, P < 0.01), and had poorer SAP scores (MD: -4.9 ± 5.2 vs. -2.6 ± 5.2 dB, P < 0.01; PSD: 4.3 ± 2.9 vs. 2.5 ± 3.0 dB, P < 0.01). By univariate analysis, mean latencies were longer in ßPPA eyes (6.1 ± 5.3 vs. 4.0 ± 5.5 ms, P < 0.01). After adjusting for differences in SE, age, and SAP MD, there was no significant difference between the two groups (P = 0.09). ßPPA eyes had lower amplitude log SNR (0.49 ± 0.16 vs. 0.56 ± 0.15, P < 0.01), which lost significance (P = 0.51) after adjusting for MD and PSD. Although eyes with ßPPA had significantly lower amplitudes and prolonged latencies than eyes without ßPPA, these differences were attributable to differences in SAP severity, age, and refractive error. Thus, ßPPA does not appear to be an independent factor affecting mfVEP responses in eyes with GON.

Beta-zone parapapillary atrophy and multifocal visual evoked potentials in eyes with glaucomatous optic neuropathy

PubMed Central

Ketner, Scott; Teng, Christopher C.; Ehrlich, Joshua R.; Raza, Ali S.; Liebmann, Jeffrey M.; Ritch, Robert; Hood, Donald C.

2015-01-01

We investigated changes in multifocal visual evoked potential (mfVEP) responses due to beta-zone parapapillary atrophy (βPPA). Patients with glaucomatous optic neuropathy (GON) with or without standard achromatic perimetry (SAP) abnormalities were referred for mfVEP testing during a 2-year period. Eyes with good quality optic disc stereophotographs and reliable SAP results were included. The mfVEP monocular mean latency delays (ms) and amplitudes (SNR) were analyzed. Age, SAP mean deviation (MD), pattern standard deviation (PSD), and spherical equivalent (SE) were analyzed in the multivariate model. Generalized estimated equations were used for comparisons between groups after adjusting for inter-eye associations. Of 394 eyes of 200 patients, 223 (57%) had βPPA. The βPPA eyes were older (59.6 ± 13.7 vs. 56.5 ± 13.7 year, P = 0.02), more myopic (−4.0 ± 3.5 vs. −1.3 ± 3.5 D, P < 0.01), and had poorer SAP scores (MD: −4.9 ± 5.2 vs. −2.6 ± 5.2 dB, P < 0.01; PSD: 4.3 ± 2.9 vs. 2.5 ± 3.0 dB, P < 0.01). By univariate analysis, mean latencies were longer in βPPA eyes (6.1 ± 5.3 vs. 4.0 ± 5.5 ms, P < 0.01). After adjusting for differences in SE, age, and SAP MD, there was no significant difference between the two groups (P = 0.09). βPPA eyes had lower amplitude log SNR (0.49 ± 0.16 vs. 0.56 ± 0.15, P < 0.01), which lost significance (P = 0.51) after adjusting for MD and PSD. Although eyes with βPPA had significantly lower amplitudes and prolonged latencies than eyes without βPPA, these differences were attributable to differences in SAP severity, age, and refractive error. Thus, βPPA does not appear to be an independent factor affecting mfVEP responses in eyes with GON. PMID:21735265

SU-E-T-248: An Extended Generalized Equivalent Uniform Dose Accounting for Dose-Range Dependency of Radio-Biological Parameters.

PubMed

Troeller, A; Soehn, M; Yan, D

2012-06-01

Introducing an extended, phenomenological, generalized equivalent uniform dose (eEUD) that incorporates multiple volume-effect parameters for different dose-ranges. The generalized EUD (gEUD) was introduced as an estimate of the EUD that incorporates a single, tissue-specific parameter - the volume-effect-parameter (VEP) 'a'. As a purely phenomenological concept, its radio-biological equivalency to a given inhomogeneous dose distribution is not a priori clear and mechanistic models based on radio-biological parameters are assumed to better resemble the underlying biology. However, for normal organs mechanistic models are hard to derive, since the structural organization of the tissue plays a significant role. Consequently, phenomenological approaches might be especially useful in order to describe dose-response for normal tissues. However, the single parameter used to estimate the gEUD may not suffice in accurately representing more complex biological effects that have been discussed in the literature. For instance, radio-biological parameters and hence the effects of fractionation are known to be dose-range dependent. Therefore, we propose an extended phenomenological eEUD formula that incorporates multiple VEPs accounting for dose-range dependency. The eEUD introduced is a piecewise polynomial expansion of the gEUD formula. In general, it allows for an arbitrary number of VEPs, each valid for a certain dose-range. We proved that the formula fulfills required mathematical and physical criteria such as invertibility of the underlying dose-effect and continuity in dose. Furthermore, it contains the gEUD as a special case, if all VEPs are equal to 'a' from the gEUD model. The eEUD is a concept that expands the gEUD such that it can theoretically represent dose-range dependent effects. Its practicality, however, remains to be shown. As a next step, this will be done by estimating the eEUD from patient data using maximum-likelihood based NTCP modelling in the same way it is commonly done for the gEUD. © 2012 American Association of Physicists in Medicine.

Pattern visual evoked potential as a predictor of occlusion therapy for amblyopia.

PubMed

Chung, Woosuk; Hong, Samin; Lee, Jong Bok; Han, Sueng-Han

2008-12-01

This study was conducted to investigate the role of the pattern visual evoked potential (pVEP) as a predictor of occlusion therapy for patients with strabismic, anisometropic, and isometropic amblyopia. The secondary aim was to compare the characteristics of pVEP between strabismic and anisometropic amblyopia. This retrospective comparative case series included 120 patients who had received occlusion therapy or a glasses prescription for correction of strabismic, anisometropic, and isometropic amblyopia (20 patients had strabismic amblyopia, 41 patients had anisometropic amblyopia, and 59 patients had isometropic amblyopia). For each patient, the value of the P100 latency on pVEP at the time of the initial diagnosis of amblyopia was collected. Subsequently, the P100 latency was compared according to types of amblyopia. Fifty of 120 patients (7 patients with strabismic amblyopia, 21 patients with anisometropic amblyopia, and 22 patients with isometropic amblyopia) who were followed-up for longer than 6 months were divided into two groups based on the value of their P100 latency (Group 1, P100 latency 120 msec or less; Group 2, P100 latency longer than 120 msec.) The amount of visual improvement after occlusion therapy or glasses was compared between two study groups. The mean P100 latency was 119.7+/-25.2 msec in eyes with strabismic amblyopia and 111.9+/-17.8 msec in eyes with non-strabismic (anisometropic or isometropic) amblyopia (p=0.213). In Group 1, the mean visual improvement after occlusion therapy or glasses was 3.69+/-2.14 lines on Dr. Hahn's standard test chart; in Group 2, the mean improvement was 2.27+/-2.21 lines (p=0.023). The P100 latency on pVEP at the time of initial diagnosis was significantly related to the visual improvement after occlusion therapy or glasses in patients with strabismic, anisometropic, and isometropic amblyopia. Therefore, it was presumed that patients with a delayed P100 latency might have less visual improvement after occlusion therapy or glasses. In addition, there was no apparent difference in P100 latency between patients with strabismic and non-strabismic (anisometropic or isometropic) amblyopia.

Differential Classical Conditioning Selectively Heightens Response Gain of Neural Population Activity in Human Visual Cortex

PubMed Central

Song, Inkyung; Keil, Andreas

2015-01-01

Neutral cues, after being reliably paired with noxious events, prompt defensive engagement and amplified sensory responses. To examine the neurophysiology underlying these adaptive changes, we quantified the contrast-response function of visual cortical population activity during differential aversive conditioning. Steady-state visual evoked potentials (ssVEPs) were recorded while participants discriminated the orientation of rapidly flickering grating stimuli. During each trial, luminance contrast of the gratings was slowly increased and then decreased. Right-tilted gratings (CS+) were paired with loud white noise but left-tilted gratings (CS−) were not. The contrast-following waveform envelope of ssVEPs showed selective amplification of the CS+ only during the high-contrast stage of the viewing epoch. Findings support the notion that motivational relevance, learned in a time frame of minutes, affects vision through a response gain mechanism. PMID:24981277

Spatial adaptation of the cortical visual evoked potential of the cat.

PubMed

Bonds, A B

1984-06-01

Adaptation that is spatially specific for the adapting pattern has been seen psychophysically in humans. This is indirect evidence for independent analyzers (putatively single units) that are specific for orientation and spatial frequency in the human visual system, but it is unclear how global adaptation characteristics may be related to single unit performance. Spatially specific adaptation was sought in the cat visual evoked potential (VEP), with a view towards relating this phenomenon with what we know of cat single units. Adaptation to sine-wave gratings results in a temporary loss of cat VEP amplitude, with induction and recovery similar to that seen in human psychophysical experiments. The amplitude loss was specific for both the spatial frequency and orientation of the adapting pattern. The bandwidth of adaptation was not unlike the average selectivity of a population of cat single units.

Possible long term effects of chemical warfare using visual evoked potentials.

PubMed

Riazi, Abbas; Hafezi, Rhamatollah; Babaei, Mahmoud; Naderi, Mostafa

2014-09-01

Some studies have already addressed the effects of occupational organic solvent exposure on the visually evoked potentials (VEPs). Visual system is an important target for Sulphur Mustard (SM) toxicity. A number of Iranian victims of Sulphur Mustard (SM) agent were apprehensive about the delay effect of SM on their vision and a possible delay effect of SM on their visual cortex. This investigation was performed on 34 individuals with a history of chemical exposure and a control group of 15 normal people. The Toennies electro-diagnosis device was used and its signals were saved as the latencies. The mean of N75, N140 and P100 of victims of chemical warfare (VCWs) and control group indicated no significant results (P>0.05). The VCWs did not show any visual symptoms and there was no clear deficit in their VEPs.

[Effect of free and polymer carrier encapsulated doxorubicin towards HCT116 cells of human colorectal carcinoma].

PubMed

Sen'kiv, Iu V; Heffeter, P; Riabtseva, A O; Boĭko, N M; Mitina, N Ie; Zaichenko, O S; Berger, W; Stoĭka, R S

2013-01-01

Development of novel nanoscale functionalized carriers is nowadays one of the most urgent problems in cancer treatment. The aim of our study was to compare the antineoplastic effect of free doxorubicin and its complex with a nanoscale polymeric carrier towards HTC116 colorectal carcinoma cells. It was established that application of the complex of poly(5-tret-butylperoxy)-5-methyl-1-hexene-3-in-co-glycydyl metacrylat)-graft-polyethyleneglycol (poly(VEP-GMA-PEG)-graft-PEG), where VEP--5-tret-butylperoxy)-5-methyl-1-hexene-3-in; GMA--glycydyl metacrylat; graft-PEG--graft-polyethyleneglycol accordingly, functionalized with phosphatidylcholine for doxorubicin delivery increased 10 times the efficiency of cytotoxic action of this drug, as compared wich such efficiency in case of the action of free doxorubicin. The encapsulated form of doxorubicin caused more intensive cleavage of the reparation enzyme PARP and longer delay in G2/M cell cycle arrest, compared to such effects of free doxorubicin. The developed carrier itself is non-toxic to the used mammalian cells and does not cause impairment in their cell cycle. A deletion in both alleles of p53 gene did not affect the antineoplastic action of doxorubicin that was immobilized on the nanoscale carrier. Thus, p53-dependent signaling pathways are not involved in the cytotoxic action of doxorubicin-carrier complex. It is suggested that novel nanoscale polymeric carrier poly(VEP-GMA-PEG)-graft-PEG functionalized with phosphatidylcholine could be a promising carrier for targeted delivery of anticancer drugs.

The locus of origin of augmenting and reducing of visual evoked potentials in rat brain.

PubMed

Siegel, J; Gayle, D; Sharma, A; Driscoll, P

1996-07-01

Humans who are high sensation seekers and cats who demonstrate comparable behavioral traits show increasing amplitudes of the early components of the cortical visual evoked potential (VEP) to increasing intensities of light flash; low sensation seekers show VEP reducing. Roman high-avoidance (RHA) and Roman low-avoidance (RLA) rats have behavioral traits comparable to human and cat high and low sensation seekers, respectively. Previously, we showed that RHA and RLA rats are cortical VEP augmenters and reducers, respectively. The goal of this study was to determine if augmenting-reducing is in fact a property of the visual cortex or if it originates at the lateral geniculate nucleus and is merely reflected in recordings from the cortex. EPs to five flash intensities were recorded from the visual cortex and dorsal lateral geniculate of RHA and RLA rats. As in the previous study, the slope of the first cortical component as a function of flash intensity was greater in the RHA than in the RLA rats. The amplitude of the geniculate component that has a latency shorter than the first cortical component was no different in the two lines of rats. The finding from the cortex confirms the earlier finding of augmenting and reducing in RHA and RLA rats, respectively. The major new finding is that the augmenting-reducing difference recorded at the cortex does not occur at the thalamus, indicating that it is truly a cortical phenomenon.

Basic visual dysfunction allows classification of patients with schizophrenia with exceptional accuracy.

PubMed

González-Hernández, J A; Pita-Alcorta, C; Padrón, A; Finalé, A; Galán, L; Martínez, E; Díaz-Comas, L; Samper-González, J A; Lencer, R; Marot, M

2014-10-01

Basic visual dysfunctions are commonly reported in schizophrenia; however their value as diagnostic tools remains uncertain. This study reports a novel electrophysiological approach using checkerboard visual evoked potentials (VEP). Sources of spectral resolution VEP-components C1, P1 and N1 were estimated by LORETA, and the band-effects (BSE) on these estimated sources were explored in each subject. BSEs were Z-transformed for each component and relationships with clinical variables were assessed. Clinical effects were evaluated by ROC-curves and predictive values. Forty-eight patients with schizophrenia (SZ) and 55 healthy controls participated in the study. For each of the 48 patients, the three VEP components were localized to both dorsal and ventral brain areas and also deviated from a normal distribution. P1 and N1 deviations were independent of treatment, illness chronicity or gender. Results from LORETA also suggest that deficits in thalamus, posterior cingulum, precuneus, superior parietal and medial occipitotemporal areas were associated with symptom severity. While positive symptoms were more strongly related to sensory processing deficits (P1), negative symptoms were more strongly related to perceptual processing dysfunction (N1). Clinical validation revealed positive and negative predictive values for correctly classifying SZ of 100% and 77%, respectively. Classification in an additional independent sample of 30 SZ corroborated these results. In summary, this novel approach revealed basic visual dysfunctions in all patients with schizophrenia, suggesting these visual dysfunctions represent a promising candidate as a biomarker for schizophrenia. Copyright © 2014 Elsevier B.V. All rights reserved.

Sequential Involvement of the Nervous System in Subacute Combined Degeneration

PubMed Central

Minn, Yang-Ki; Kim, Seung-Min; Kim, Se-Hoon; Kwon, Ki-Han

2012-01-01

Purpose Subacute combined degeneration (SCD) involves progressive degeneration of the spinal cord, optic nerve, and peripheral nerves. Vitamin B12 (VB12) is a co-factor in myelin synthesis. Because each cell that constitutes the myelin component in the central nervous system and peripheral nervous system is different, it is improbable that these cells undergo simultaneous degeneration. However, the sequence of degeneration in SCD has not been established. Materials and Methods In this study, we analysed medical records and electrophysiological data of patients who showed neurological symptoms and whose serum VB12 levels were lower than 200 pg/mL. Results We enrolled 49 patients in this study. Their mean VB12 level was 68.3 pg/mL. Somatosensory evoked potential (SEP) study showed abnormal findings in 38 patients. Of the 40 patients who underwent visual evoked potential (VEP) study, 14 showed abnormal responses. Eighteen patients showed abnormal findings on a nerve conduction study (NCS). In this study, abnormal posterior tibial nerve SEPs only were seen in 16 patients, median nerve SEPs only were seen in 3 patients, abnormal VEPs only in two, and abnormal NCS responses in one patient. No patient complained of cognitive symptoms. Conclusion In SCD, degeneration appears to progress in the following order: lower spinal cord, cervical spinal cord, peripheral nerve/optic nerve, and finally, the brain. PMID:22318813

Abnormal late visual responses and alpha oscillations in neurofibromatosis type 1: a link to visual and attention deficits

PubMed Central

2014-01-01

Background Neurofibromatosis type 1 (NF1) affects several areas of cognitive function including visual processing and attention. We investigated the neural mechanisms underlying the visual deficits of children and adolescents with NF1 by studying visual evoked potentials (VEPs) and brain oscillations during visual stimulation and rest periods. Methods Electroencephalogram/event-related potential (EEG/ERP) responses were measured during visual processing (NF1 n = 17; controls n = 19) and idle periods with eyes closed and eyes open (NF1 n = 12; controls n = 14). Visual stimulation was chosen to bias activation of the three detection mechanisms: achromatic, red-green and blue-yellow. Results We found significant differences between the groups for late chromatic VEPs and a specific enhancement in the amplitude of the parieto-occipital alpha amplitude both during visual stimulation and idle periods. Alpha modulation and the negative influence of alpha oscillations in visual performance were found in both groups. Conclusions Our findings suggest abnormal later stages of visual processing and enhanced amplitude of alpha oscillations supporting the existence of deficits in basic sensory processing in NF1. Given the link between alpha oscillations, visual perception and attention, these results indicate a neural mechanism that might underlie the visual sensitivity deficits and increased lapses of attention observed in individuals with NF1. PMID:24559228

Influence of visual angle on pattern reversal visual evoked potentials

PubMed Central

Kothari, Ruchi; Singh, Smita; Singh, Ramji; Shukla, A. K.; Bokariya, Pradeep

2014-01-01

Purpose: The aim of this study was to find whether the visual evoked potential (VEP) latencies and amplitude are altered with different visual angles in healthy adult volunteers or not and to determine the visual angle which is the optimum and most appropriate among a wide range of check sizes for the reliable interpretation of pattern reversal VEPs (PRVEPs). Materials and Methods: The present study was conducted on 40 healthy volunteers. The subjects were divided into two groups. One group consisted of 20 individuals (nine males and 11 females) in the age range of 25-57 years and they were exposed to checks subtending a visual angle of 90, 120, and 180 minutes of arc. Another group comprised of 20 individuals (10 males and 10 females) in the age range of 36-60 years and they were subjected to checks subtending a visual angle of 15, 30, and 120 minutes of arc. The stimulus configuration comprised of the transient pattern reversal method in which a black and white checker board is generated (full field) on a VEP Monitor by an Evoked Potential Recorder (RMS EMG. EPMARK II). The statistical analysis was done by One Way Analysis of Variance (ANOVA) using EPI INFO 6. Results: In Group I, the maximum (max.) P100 latency of 98.8 ± 4.7 and the max. P100 amplitude of 10.05 ± 3.1 μV was obtained with checks of 90 minutes. In Group II, the max. P100 latency of 105.19 ± 4.75 msec as well as the max. P100 amplitude of 8.23 ± 3.30 μV was obtained with 15 minutes. The min. P100 latency in both the groups was obtained with checks of 120 minutes while the min. P100 amplitude was obtained with 180 minutes. A statistically significant difference was derived between means of P100 latency for 15 and 30 minutes with reference to its value for 120 minutes and between the mean value of P100 amplitude for 120 minutes and that of 90 and 180 minutes. Conclusion: Altering the size of stimulus (visual angle) has an effect on the PRVEP parameters. Our study found that the 120 is the appropriate (and optimal) check size that can be used for accurate interpretation of PRVEPs. This will help in better assessment of the optic nerve function and integrity of anterior visual pathways. PMID:25378875

Delayed P100-Like Latencies in Multiple Sclerosis: A Preliminary Investigation Using Visual Evoked Spread Spectrum Analysis

PubMed Central

Kiiski, Hanni S. M.; Ní Riada, Sinéad; Lalor, Edmund C.; Gonçalves, Nuno R.; Nolan, Hugh; Whelan, Robert; Lonergan, Róisín; Kelly, Siobhán; O'Brien, Marie Claire; Kinsella, Katie; Bramham, Jessica; Burke, Teresa; Ó Donnchadha, Seán; Hutchinson, Michael; Tubridy, Niall; Reilly, Richard B.

2016-01-01

Conduction along the optic nerve is often slowed in multiple sclerosis (MS). This is typically assessed by measuring the latency of the P100 component of the Visual Evoked Potential (VEP) using electroencephalography. The Visual Evoked Spread Spectrum Analysis (VESPA) method, which involves modulating the contrast of a continuous visual stimulus over time, can produce a visually evoked response analogous to the P100 but with a higher signal-to-noise ratio and potentially higher sensitivity to individual differences in comparison to the VEP. The main objective of the study was to conduct a preliminary investigation into the utility of the VESPA method for probing and monitoring visual dysfunction in multiple sclerosis. The latencies and amplitudes of the P100-like VESPA component were compared between healthy controls and multiple sclerosis patients, and multiple sclerosis subgroups. The P100-like VESPA component activations were examined at baseline and over a 3-year period. The study included 43 multiple sclerosis patients (23 relapsing-remitting MS, 20 secondary-progressive MS) and 42 healthy controls who completed the VESPA at baseline. The follow-up sessions were conducted 12 months after baseline with 24 MS patients (15 relapsing-remitting MS, 9 secondary-progressive MS) and 23 controls, and again at 24 months post-baseline with 19 MS patients (13 relapsing-remitting MS, 6 secondary-progressive MS) and 14 controls. The results showed P100-like VESPA latencies to be delayed in multiple sclerosis compared to healthy controls over the 24-month period. Secondary-progressive MS patients had most pronounced delay in P100-like VESPA latency relative to relapsing-remitting MS and controls. There were no longitudinal P100-like VESPA response differences. These findings suggest that the VESPA method is a reproducible electrophysiological method that may have potential utility in the assessment of visual dysfunction in multiple sclerosis. PMID:26726800

Repeatability of short-duration transient visual evoked potentials in normal subjects.

PubMed

Tello, Celso; De Moraes, Carlos Gustavo V; Prata, Tiago S; Derr, Peter; Patel, Jayson; Siegfried, John; Liebmann, Jeffrey M; Ritch, Robert

2010-06-01

To evaluate the within-session and inter-session repeatability of a new, short-duration transient visual evoked potential (SD-tVEP) device on normal individuals, we tested 30 normal subjects (20/20 visual acuity, normal 24-2 SITA Standard VF) with SD-tVEP. Ten of these subjects had their tests repeated within 1-2 months from the initial visit. Synchronized single-channel EEG was recorded using a modified Diopsys Enfant System (Diopsys, Inc., Pine Brook, New Jersey, USA). A checkerboard stimulus was modulated at two reversals per second. Two different contrasts of checkerboard reversal patterns were used: 85% Michelson contrast with a mean luminance of 66.25 cd/m(2) and 10% Michelson contrast with a mean luminance of 112 cd/m(2). Each test lasted 20 s. Both eyes, independently and together, were tested 10 times (5 times at each contrast level). The following information was identified from the filtered N75-P100-N135 complex: N75 amplitude, N75 latency, P100 amplitude, P100 latency, and Delta Amplitude (N75-P100). The median values for each eye's five SD-tVEP parameters were calculated and grouped into two data sets based on contrast level. Mean age was 27.3 +/- 5.2 years. For OD only, the median (95% confidence intervals) of Delta Amplitude (N75-P100) amplitudes at 10% and 85% contrast were 4.6 uV (4.1-5.9) and 7.1 uV (5.15-9.31). The median P100 latencies were 115.2 ms (112.0-117.7) and 104.0 ms (99.9-106.0). There was little within-session variability for any of these parameters. Intraclass correlation coefficients ranged between 0.64 and 0.98, and within subject coefficients of variation were 3-5% (P100 latency) and 15-30% (Delta Amplitude (N75-P100) amplitude). Bland-Altman plots showed good agreement between the first and fifth test sessions (85% contrast Delta Amplitude (N75-P100) delta amplitude, mean difference, 0.48 mV, 95% CI, -0.18-1.12; 85% contrast P100 latency delay, -0.82 ms, 95% CI, -3.12-1.46; 10% contrast Delta Amplitude (N75-P100) amplitude, 0.58 mV, 95% CI, -0.27-1.45; 10% contrast P100 latency delay, -2.05 mV, 95% CI, -5.12-1.01). The inter-eye correlation and agreement were significant for both SD-tVEP amplitude and P100 latency measurements. For the subset of eyes in which the inter-session repeatability was tested, the intraclass correlation coefficients ranged between 0.71 and 0.86 with good agreement shown on Bland-Altman plots. Short-duration transient VEP technology showed good within-session, inter-session repeatability, and good inter-eye correlation and agreement.

Sight and blindness in the same person: Gating in the visual system.

PubMed

Strasburger, Hans; Waldvogel, Bruno

2015-12-01

We present the case of a patient having dissociative identity disorder (DID) who-after 15 years of misdiagnosed cortical blindness--step-by-step regained sight during psychotherapeutic treatment. At first only a few personality states regained vision whereas others remained blind. This could be confirmed by electrophysiological measurement, in which visual evoked potentials (VEPs) were absent in the blind personality states but were normal and stable in the seeing states. A switch between these states could happen within seconds. We assume a top-down modulation of activity in the primary visual pathway as a neural basis of such psychogenic blindness, possibly at the level of the thalamus. VEPs therefore do not allow separating psychogenic blindness from organic disruption of the visual pathway. In summary, psychogenic blindness seems to suppress visual information at an early neural stage. © 2015 The Institute of Psychology, Chinese Academy of Sciences and Wiley Publishing Asia Pty Ltd.

Bilateral retrobulbar optic neuropathy as the only sign of zoledronic acid toxicity.

PubMed

Lavado, Félix Manco; Prieto, Marta Para; Osorio, María Rosalba Ramoa; Gálvez, María Isabel López; Leal, Lucía Manzanas

2017-10-01

Bisphosphonates may rarely cause ocular adverse effects and retrobulbar optic neuropathy (RON) secondary to zoledronic acid is very rare. A 67-year-old man was referred because of progressive and painless decrease vision in the left eye. He had been treated with 7 cycles of zoledronic acid infusions because of metastatic prostate cancer. On examination, VA was 20/20 in the right eye (OD) and 20/50 in the left eye (OS). The optic nerve was unremarkable OU. Pattern visual evoked potentials (pVEP) and electroretinography were performed with the result of VEP responses abolished in OS, and the VEP waveform within the normal range amplitude and delayed peak latencies in OD. Due to the high suspicion of bilateral RON secondary to zoledronic acid, we decided to discontinue the treatment. Two months later, VA was 20/20 OD and hand motions OS, with relative afferent pupillary defect and a pallor of the optic disc in OS. The diagnosis of bilateral RON secondary to zoledronic acid infusions was confirmed, and it was only partially reversible. Zoledronic acid is a potent new generation bisphosphonate increasingly used in oncologic patients and it is usually well tolerated. Optic nerve toxicity is not a side effect recognised by either the Food and Drug Administration or the drug manufacturers, and to our knowledge, this is the first case of zoledronic acid-related bilateral RON with late onset. In conclusion, patients treated with bisphosphonates should be informed about the possibility of ocular side-effects, and ophthalmologists should be consider discontinuing the drug. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of callosal transfer on visual cortical evoked response and the implication in the development of a visual prosthesis.

PubMed

Siu, Timothy L; Morley, John W

2007-12-01

The development of a visual prosthesis has been limited by an incomplete understanding of functional changes of the visual cortex accompanying deafferentation. In particular, the role of the corpus callosum in modulating these changes has not been fully evaluated. Recent experimental evidence suggests that through synaptic modulation, short-term (4-5 days) visual deafferentation can induce plastic changes in the visual cortex, leading to adaptive enhancement of residual visual input. We therefore investigated whether a compensatory rerouting of visual information can occur via the indirect transcallosal linkage after deafferentation and the influence of this interhemispheric communication on the visual evoked response of each hemisphere. In albino rabbits, misrouting of uncrossed optic fibres reduces ipsilateral input to a negligible degree. We thus took advantage of this congenital anomaly to model unilateral cortical and ocular deafferentation by eliminating visual input from one eye and recorded the visual evoked potential (VEP) from the intact eye. In keeping with the chiasmal anomaly, no VEP was elicited from the hemisphere ipsilateral to the intact eye. This remained unchanged following unilateral visual deafferentation. The amplitude and latency of the VEP in the fellow hemisphere, however, were significantly decreased in the deafferented animals. Our data suggest that callosal linkage does not contribute to visual evoked responses and this is not changed after short-term deafferentation. The decrease in amplitude and latency of evoked responses in the hemisphere ipsilateral to the treated eye, however, confirms the facilitatory role of callosal transfer. This observation highlights the importance of bicortical stimulation in the future design of a cortical visual prosthesis.

An unexpected target of spinal direct current stimulation: Interhemispheric connectivity in humans.

PubMed

Bocci, Tommaso; Caleo, Matteo; Vannini, Beatrice; Vergari, Maurizio; Cogiamanian, Filippo; Rossi, Simone; Priori, Alberto; Sartucci, Ferdinando

2015-10-30

Transcutaneous spinal Direct Current Stimulation (tsDCS) is a noninvasive technique based on the application of weak electrical currents over spinal cord. We studied the effects of tsDCS on interhemispheric motor connectivity and visual processing by evaluating changes in ipsilateral Silent Period (iSP), Transcallosal Conduction Time (TCT) and hemifield Visual Evoked Potentials (hVEPs), before (T0) and at a different intervals following sham, anodal and cathodal tsDCS (T9-T11 level, 2.0 mA, 20'). Motor Evoked Potentials (MEPs) were recorded from abductor pollicis brevis (APB), abductor hallucis (AH) and deltoid muscles. hVEPs were recorded bilaterally by reversal of a horizontal square wave grating with the display positioned in the right hemifield. Anodal tsDCS increased TCT (p < 0.001) and the interhemispheric delay for both the main VEP components (N1: p = 0.0003; P1: p < 0.0001), dampening at the same time iSP duration (APB: p < 0.0001; AH: p = 0.0005; deltoid: p < 0.0001), while cathodal stimulation elicited opposite effects (p < 0.0001). tsDCS modulates interhemispheric processing in a polarity-specific manner, with anodal stimulation leading to a functional disconnection between hemispheres. tsDCS would be a new promising therapeutic tool in managing a number of human diseases characterized by an impaired interhemispheric balance, or an early rehabilitation strategy in patients with acute brain lesions, when other non-invasive brain stimulation techniques (NIBS) are not indicated due to safety concerns. Copyright © 2015 Elsevier B.V. All rights reserved.

Colour vision and contrast sensitivity losses of mercury intoxicated industry workers in Brazil.

PubMed

Ventura, D F; Simões, A L; Tomaz, S; Costa, M F; Lago, M; Costa, M T V; Canto-Pereira, L H M; de Souza, J M; Faria, M A M; Silveira, L C L

2005-05-01

We evaluated vision loss in workers from fluorescent lamp industries (n=39) who had retired due to intoxication with mercury vapour and had been away from the work situation for several years (mean=6.32 years). An age-matched control group was submitted to the same tests for comparison. The luminance contrast sensitivity (CSF) was measured psychophysically and with the sweep visual evoked potential (sVEP) method. Chromatic red-green and blue-yellow CSFs were measured psychophysically. Colour discrimination was assessed with the Farnsworth-Munsell 100-hue test, Lanthony D-15d test and Cambridge Colour Vision Test. Patient data showed significantly lower scores in all colour tests compared to controls (p<.001). The behavioural luminance CSF of the patients was lower than that of controls (p<.001 at all frequencies tested). This result was confirmed by the electrophysiologically measured sweep VEP luminance CSF except at the highest frequencies-a difference that might be related to stimulus differences in the two situations. Chromatic CSFs were also statistically significantly lower for the patients than for the controls, for both chromatic equiluminant stimuli: red-green (p<.005) and blue-yellow (p<.04 for all frequencies, except 2 cycles per degree (cpd), the highest spatial frequency tested) spatial gratings. We conclude that exposure to elemental mercury vapour is associated with profound and lasting losses in achromatic and chromatic visual functions, affecting the magno-, parvo- and koniocellular visual pathways.

The Vital@Work Study. The systematic development of a lifestyle intervention to improve older workers' vitality and the design of a randomised controlled trial evaluating this intervention

PubMed Central

Strijk, Jorien E; Proper, Karin I; van der Beek, Allard J; van Mechelen, Willem

2009-01-01

Background A major contributor of early exit from work is a decline in health with increasing age. As healthy lifestyle choices contribute to better health outcomes, an intervention aimed at an improved lifestyle is considered a potentially effective tool to keep older workers healthy and vital, and thereby to prolong labour participation. Methods Using the Intervention Mapping (IM) protocol, a lifestyle intervention was developed based on information obtained from 1) literature, 2) a short lifestyle questionnaire aimed at indentifying the lifestyle behaviours among the target group, and 3) focusgroup (FG) interviews among 36 older workers (aged 45+ years) aimed at identifying: a) key determinants of lifestyle behaviour, b) a definition of vitality, and c) ideas about how vitality can be improved by lifestyle. The main lifestyle problems identified were: insufficient levels of physical activity and insufficient intake of fruit and vegetables. Using information from both literature and FG interviews, vitality consists of a mental and a physical component. The interviewees suggested to improve the mental component of vitality by means of relaxation exercises (e.g. yoga); physical vitality could be improved by aerobic endurance exercise and strength training. The lifestyle intervention (6 months) consists of three visits to a Personal Vitality Coach (PVC) combined with a Vitality Exercise Programme (VEP). The VEP consists of: 1) once a week a guided yoga group session aimed at relaxation exercises, 2) once a week a guided aerobic workout group session aimed at improving aerobic fitness and increasing muscle strength, and 3) older workers will be asked to perform once a week for at least 45 minutes vigorous physical activity without face-to-face instructions (e.g. fitness). Moreover, free fruit will be offered at the group sessions of the VEP. The lifestyle intervention will be evaluated in a RCT among older workers of two major academic hospitals in the Netherlands. At baseline, after 6 and 12 months, measurements (primary: lifestyle and vitality, and secondary: work-engagement and productivity) will take place. Discussion The lifestyle programme is developed specifically tailored to the needs of the older workers and which is aimed at improving their vitality. Trial registration NTR1240 PMID:19903345

Assessment of visual disability using visual evoked potentials

PubMed Central

2012-01-01

Background The purpose of this study is to validate the use of visual evoked potential (VEP) to objectively quantify visual acuity in normal and amblyopic patients, and determine if it is possible to predict visual acuity in disability assessment to register visual pathway lesions. Methods A retrospective chart review was conducted of patients diagnosed with normal vision, unilateral amblyopia, optic neuritis, and visual disability who visited the university medical center for registration from March 2007 to October 2009. The study included 20 normal subjects (20 right eyes: 10 females, 10 males, ages 9–42 years), 18 unilateral amblyopic patients (18 amblyopic eyes, ages 19–36 years), 19 optic neuritis patients (19 eyes: ages 9–71 years), and 10 patients with visual disability having visual pathway lesions. Amplitude and latencies were analyzed and correlations with visual acuity (logMAR) were derived from 20 normal and 18 amblyopic subjects. Correlation of VEP amplitude and visual acuity (logMAR) of 19 optic neuritis patients confirmed relationships between visual acuity and amplitude. We calculated the objective visual acuity (logMAR) of 16 eyes from 10 patients to diagnose the presence or absence of visual disability using relations derived from 20 normal and 18 amblyopic eyes. Results Linear regression analyses between amplitude of pattern visual evoked potentials and visual acuity (logMAR) of 38 eyes from normal (right eyes) and amblyopic (amblyopic eyes) subjects were significant [y = −0.072x + 1.22, x: VEP amplitude, y: visual acuity (logMAR)]. There were no significant differences between visual acuity prediction values, which substituted amplitude values of 19 eyes with optic neuritis into function. We calculated the objective visual acuity of 16 eyes of 10 patients to diagnose the presence or absence of visual disability using relations of y = −0.072x + 1.22 (−0.072). This resulted in a prediction reference of visual acuity associated with malingering vs. real disability in a range >5.77 μV. The results could be useful, especially in cases of no obvious pale disc with trauma. Conclusions Visual acuity quantification using absolute value of amplitude in pattern visual evoked potentials was useful in confirming subjective visual acuity for cutoff values >5.77 μV in disability evaluation to discriminate the malingering from real disability. PMID:22866948

Single-trial detection of visual evoked potentials by common spatial patterns and wavelet filtering for brain-computer interface.

PubMed

Tu, Yiheng; Huang, Gan; Hung, Yeung Sam; Hu, Li; Hu, Yong; Zhang, Zhiguo

2013-01-01

Event-related potentials (ERPs) are widely used in brain-computer interface (BCI) systems as input signals conveying a subject's intention. A fast and reliable single-trial ERP detection method can be used to develop a BCI system with both high speed and high accuracy. However, most of single-trial ERP detection methods are developed for offline EEG analysis and thus have a high computational complexity and need manual operations. Therefore, they are not applicable to practical BCI systems, which require a low-complexity and automatic ERP detection method. This work presents a joint spatial-time-frequency filter that combines common spatial patterns (CSP) and wavelet filtering (WF) for improving the signal-to-noise (SNR) of visual evoked potentials (VEP), which can lead to a single-trial ERP-based BCI.

Neural Correlates of Expert Visuomotor Performance in Badminton Players.

PubMed

Hülsdünker, Thorben; Strüder, Heiko K; Mierau, Andreas

2016-11-01

Elite/skilled athletes participating in sports that require the initiation of targeted movements in response to visual cues under critical time pressure typically outperform nonathletes in a visuomotor reaction task. However, the exact physiological mechanisms of this advantage remain unclear. Therefore, this study aimed to determine the neurophysiological processes contributing to superior visuomotor performance in athletes using visual evoked potential (VEP). Central and peripheral determinants of visuomotor reaction time were investigated in 15 skilled badminton players and 28 age-matched nonathletic controls. To determine the speed of visual signal perception in the cortex, chromatic and achromatic pattern reversal stimuli were presented, and VEP values were recorded with a 64-channel EEG system. Further, a simple visuomotor reaction task was performed to investigate the transformation of the visual into a motor signal in the brain as well as the timing of muscular activation. Amplitude and latency of VEP (N75, P100, and N145) revealed that the athletes did not significantly differ from the nonathletes. However, visuomotor reaction time was significantly reduced in the athletes compared with nonathletes (athletes = 234.9 ms, nonathletes = 260.3 ms, P = 0.015). This was accompanied by an earlier activation of the premotor and supplementary motor areas (athletes = 163.9 ms, nonathletes = 199.1 ms, P = 0.015) as well as an earlier EMG onset (athletes = 167.5 ms, nonathletes = 206.5 ms, P < 0.001). The latency of premotor and supplementary motor area activation was correlated with EMG onset (r = 0.41) and visuomotor reaction time (r = 0.43). The results of this study indicate that superior visuomotor performance in athletes originates from faster visuomotor transformation in the premotor and supplementary motor cortical regions rather than from earlier perception of visual signals in the visual cortex.

The developmental effects of extremely low frequency electric fields on visual and somatosensory evoked potentials in adult rats.

PubMed

Gok, Deniz Kantar; Akpinar, Deniz; Hidisoglu, Enis; Ozen, Sukru; Agar, Aysel; Yargicoglu, Piraye

2016-01-01

The purpose of our study was to investigate the developmental effects of extremely low frequency electric fields (ELF-EFs) on visual evoked potentials (VEPs) and somatosensory-evoked potentials (SEPs) and to examine the relationship between lipid peroxidation and changes of these potentials. In this context, thiobarbituric acid reactive substances (TBARS) levels were determined as an indicator of lipid peroxidation. Wistar albino female rats were divided into four groups; Control (C), gestational (prenatal) exposure (Pr), gestational+ postnatal exposure (PP) and postnatal exposure (Po) groups. Pregnant rats of Pr and PP groups were exposed to 50 Hz electric field (EF) (12 kV/m; 1 h/day), while those of C and Po groups were placed in an inactive system during pregnancy. Following parturition, rats of PP and Po groups were exposed to ELF-EFs whereas rats of C and Pr groups were kept under the same experimental conditions without being exposed to any EF during 68 days. On postnatal day 90, rats were prepared for VEP and SEP recordings. The latencies of VEP components in all experimental groups were significantly prolonged versus C group. For SEPs, all components of PP group, P2, N2 components of Pr group and P1, P2, N2 components of Po group were delayed versus C group. As brain TBARS levels were significantly increased in Pr and Po groups, retina TBARS levels were significantly elevated in all experimental groups versus C group. In conclusion, alterations seen in evoked potentials, at least partly, could be explained by lipid peroxidation in the retina and brain.

Infant VEPs reveal neural correlates of implicit naming: Lateralized differences between lexicalized versus name-unknown pictures.

PubMed

Styles, Suzy J; Plunkett, Kim; Duta, Mihaela D

2015-10-01

Recent behavioural studies with toddlers have demonstrated that simply viewing a picture in silence triggers a cascade of linguistic processing which activates a representation of the picture's name (Mani and Plunkett, 2010, 2011). Electrophysiological studies have also shown that viewing a picture modulates the auditory evoked potentials (AEPs) triggered by later speech, from early in the second year of life (Duta et al., 2012; Friedrich and Friederici, 2005; Mani et al., 2011) further supporting the notion that picture viewing gives rise to a representation of the picture's name against which later speech can be matched. However, little is known about how and when the implicit name arises during picture viewing, or about the electrophysiological activity which supports this linguistic process. We report differences in the visual evoked potentials (VEPs) of fourteen-month-old infants who saw photographs of animals and objects, some of which were name-known (lexicalized), while waiting for an auditory label to be presented. During silent picture viewing, lateralized neural activity was selectively triggered by lexicalized items, as compared to nameless items. Lexicalized items generated a short-lasting negative-going deflection over frontal, left centro-temporal, and left occipital regions shortly after the picture appeared (126-225 ms). A positive deflection was also observed over the right hemisphere (particularly centro-temporal regions) in a later, longer-lasting window (421-720 ms). The lateralization of these differences in the VEP suggests the possible involvement of linguistic processes during picture viewing, and may reflect activity involved in the implicit activation of the picture's name. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Infant VEPs reveal neural correlates of implicit naming: Lateralized differences between lexicalized versus name-unknown pictures

PubMed Central

Styles, Suzy J.; Plunkett, Kim; Duta, Mihaela D.

2015-01-01

Recent behavioural studies with toddlers have demonstrated that simply viewing a picture in silence triggers a cascade of linguistic processing which activates a representation of the picture’s name (Mani and Plunkett, 2010, 2011). Electrophysiological studies have also shown that viewing a picture modulates the auditory evoked potentials (AEPs) triggered by later speech, from early in the second year of life (Duta et al., 2012; Friedrich and Friederici, 2005; Mani et al., 2011) further supporting the notion that picture viewing gives rise to a representation of the picture’s name against which later speech can be matched. However, little is known about how and when the implicit name arises during picture viewing, or about the electrophysiological activity which supports this linguistic process. We report differences in the visual evoked potentials (VEPs) of fourteen-month-old infants who saw photographs of animals and objects, some of which were name-known (lexicalized), while waiting for an auditory label to be presented. During silent picture viewing, lateralized neural activity was selectively triggered by lexicalized items, as compared to nameless items. Lexicalized items generated a short-lasting negative-going deflection over frontal, left centro-temporal, and left occipital regions shortly after the picture appeared (126–225 ms). A positive deflection was also observed over the right hemisphere (particularly centro-temporal regions) in a later, longer-lasting window (421–720 ms). The lateralization of these differences in the VEP suggests the possible involvement of linguistic processes during picture viewing, and may reflect activity involved in the implicit activation of the picture’s name. PMID:26232744

What does the dot-probe task measure? A reverse correlation analysis of electrocortical activity.

PubMed

Thigpen, Nina N; Gruss, L Forest; Garcia, Steven; Herring, David R; Keil, Andreas

2018-06-01

The dot-probe task is considered a gold standard for assessing the intrinsic attentive selection of one of two lateralized visual cues, measured by the response time to a subsequent, lateralized response probe. However, this task has recently been associated with poor reliability and conflicting results. To resolve these discrepancies, we tested the underlying assumption of the dot-probe task-that fast probe responses index heightened cue selection-using an electrophysiological measure of selective attention. Specifically, we used a reverse correlation approach in combination with frequency-tagged steady-state visual potentials (ssVEPs). Twenty-one participants completed a modified dot-probe task in which each member of a pair of lateralized face cues, varying in emotional expression (angry-angry, neutral-angry, neutral-neutral), flickered at one of two frequencies (15 or 20 Hz), to evoke ssVEPs. One cue was then replaced by a response probe, and participants indicated the probe orientation (0° or 90°). We analyzed the ssVEP evoked by the cues as a function of response speed to the subsequent probe (i.e., a reverse correlation analysis). Electrophysiological measures of cue processing varied with probe hemifield location: Faster responses to left probes were associated with weak amplification of the preceding left cue, apparent only in a median split analysis. By contrast, faster responses to right probes were systematically and parametrically predicted by diminished visuocortical selection of the preceding right cue. Together, these findings highlight the poor validity of the dot-probe task, in terms of quantifying intrinsic, nondirected attentive selection irrespective of probe/cue location. © 2018 Society for Psychophysiological Research.

Multifocal visual evoked responses to dichoptic stimulation using virtual reality goggles: Multifocal VER to dichoptic stimulation.

PubMed

Arvind, Hemamalini; Klistorner, Alexander; Graham, Stuart L; Grigg, John R

2006-05-01

Multifocal visual evoked potentials (mfVEPs) have demonstrated good diagnostic capabilities in glaucoma and optic neuritis. This study aimed at evaluating the possibility of simultaneously recording mfVEP for both eyes with dichoptic stimulation using virtual reality goggles and also to determine the stimulus characteristics that yield maximum amplitude. ten healthy volunteers were recruited and temporally sparse pattern pulse stimuli were presented dichoptically using virtual reality goggles. Experiment 1 involved recording responses to dichoptically presented checkerboard stimuli and also confirming true topographic representation by switching off specific segments. Experiment 2 involved monocular stimulation and comparison of amplitude with Experiment 1. In Experiment 3, orthogonally oriented gratings were dichoptically presented. Experiment 4 involved dichoptic presentation of checkerboard stimuli at different levels of sparseness (5.0 times/s, 2.5 times/s, 1.66 times/s and 1.25 times/s), where stimulation of corresponding segments of two eyes were separated by 16.7, 66.7,116.7 & 166.7 ms respectively. Experiment 1 demonstrated good traces in all regions and confirmed topographic representation. However, there was suppression of amplitude of responses to dichoptic stimulation by 17.9+/-5.4% compared to monocular stimulation. Experiment 3 demonstrated similar suppression between orthogonal and checkerboard stimuli (p = 0.08). Experiment 4 demonstrated maximum amplitude and least suppression (4.8%) with stimulation at 1.25 times/s with 166.7 ms separation between eyes. It is possible to record mfVEP for both eyes during dichoptic stimulation using virtual reality goggles, which present binocular simultaneous patterns driven by independent sequences. Interocular suppression can be almost eliminated by using a temporally sparse stimulus of 1.25 times/s with a separation of 166.7 ms between stimulation of corresponding segments of the two eyes.

[Sound improves distinction of low intensities of light in the visual cortex of a rabbit].

PubMed

Polianskiĭ, V B; Alymkulov, D E; Evtikhin, D V; Chernyshev, B V

2011-01-01

Electrodes were implanted into cranium above the primary visual cortex of four rabbits (Orictolagus cuniculus). At the first stage, visual evoked potentials (VEPs) were recorded in response to substitution of threshold visual stimuli (0.28 and 0.31 cd/m2). Then the sound (2000 Hz, 84 dB, duration 40 ms) was added simultaneously to every visual stimulus. Single sounds (without visual stimuli) did not produce a VEP-response. It was found that the amplitude ofVEP component N1 (85-110 ms) in response to complex stimuli (visual and sound) increased 1.6 times as compared to "simple" visual stimulation. At the second stage, paired substitutions of 8 different visual stimuli (range 0.38-20.2 cd/m2) by each other were performed. Sensory spaces of intensity were reconstructed on the basis of factor analysis. Sensory spaces of complexes were reconstructed in a similar way for simultaneous visual and sound stimulation. Comparison of vectors representing the stimuli in the spaces showed that the addition of a sound led to a 1.4-fold expansion of the space occupied by smaller intensities (0.28; 1.02; 3.05; 6.35 cd/m2). Also, the addition of the sound led to an arrangement of intensities in an ascending order. At the same time, the sound 1.33-times narrowed the space of larger intensities (8.48; 13.7; 16.8; 20.2 cd/m2). It is suggested that the addition of a sound improves a distinction of smaller intensities and impairs a dis- tinction of larger intensities. Sensory spaces revealed by complex stimuli were two-dimensional. This fact can be a consequence of integration of sound and light in a unified complex at simultaneous stimulation.

Repetitive Transcranial Direct Current Stimulation Induced Excitability Changes of Primary Visual Cortex and Visual Learning Effects-A Pilot Study.

PubMed

Sczesny-Kaiser, Matthias; Beckhaus, Katharina; Dinse, Hubert R; Schwenkreis, Peter; Tegenthoff, Martin; Höffken, Oliver

2016-01-01

Studies on noninvasive motor cortex stimulation and motor learning demonstrated cortical excitability as a marker for a learning effect. Transcranial direct current stimulation (tDCS) is a non-invasive tool to modulate cortical excitability. It is as yet unknown how tDCS-induced excitability changes and perceptual learning in visual cortex correlate. Our study aimed to examine the influence of tDCS on visual perceptual learning in healthy humans. Additionally, we measured excitability in primary visual cortex (V1). We hypothesized that anodal tDCS would improve and cathodal tDCS would have minor or no effects on visual learning. Anodal, cathodal or sham tDCS were applied over V1 in a randomized, double-blinded design over four consecutive days (n = 30). During 20 min of tDCS, subjects had to learn a visual orientation-discrimination task (ODT). Excitability parameters were measured by analyzing paired-stimulation behavior of visual-evoked potentials (ps-VEP) and by measuring phosphene thresholds (PTs) before and after the stimulation period of 4 days. Compared with sham-tDCS, anodal tDCS led to an improvement of visual discrimination learning (p < 0.003). We found reduced PTs and increased ps-VEP ratios indicating increased cortical excitability after anodal tDCS (PT: p = 0.002, ps-VEP: p = 0.003). Correlation analysis within the anodal tDCS group revealed no significant correlation between PTs and learning effect. For cathodal tDCS, no significant effects on learning or on excitability could be seen. Our results showed that anodal tDCS over V1 resulted in improved visual perceptual learning and increased cortical excitability. tDCS is a promising tool to alter V1 excitability and, hence, perceptual visual learning.

T(2)-weighted microMRI and evoked potential of the visual system measurements during the development of hypomyelinated transgenic mice.

PubMed

Martin, Melanie; Reyes, Samuel D; Hiltner, Timothy D; Givogri, M Irene; Tyszka, J Michael; Fisher, Robin; Campagnoni, Anthony T; Fraser, Scott E; Jacobs, Russell E; Readhead, Carol

2007-02-01

Our objective was to follow the course of a dysmyelinating disease followed by partial recovery in transgenic mice using non-invasive high-resolution (117 x 117 x 70 microm) magnetic resonance (microMRI) and evoked potential of the visual system (VEP) techniques. We used JOE (for J37 golli overexpressing) transgenic mice engineered to overexpress golli J37, a product of the Golli-mbp gene complex, specifically in oligodendrocytes. Individual JOE transgenics and their unaffected siblings were followed from 21 until 75-days-old using non-invasive in vivo VEPs and 3D T2-weighted microMRI on an 11.7 T scanner, performing what we believe is the first longitudinal study of its kind. The microMRI data indicated clear, global hypomyelination during the period of peak myelination (21-42 days), which was partially corrected at later ages (>60 days) in the JOE mice compared to controls. These microMRI data correlated well with [Campagnoni AT (1995) "Molecular biology of myelination". In: Ransom B, Kettenmann H (eds) Neuroglia--a Treatise. Oxford University Press, London, pp 555-570] myelin staining, [Campagnoni AT, Macklin WB (1988) Cellular and molecular aspects of myelin protein gene-expression. Mol Neurobiol 2:41-89] a transient intention tremor during the peak period of myelination, which abated at later ages, and [Lees MB, Brostoff SW (1984) Proteins in myelin. In: Morell (ed) Myelin. Plenum Press, New York and London, pp 197-224] VEPs which all indicated a significant delay of CNS myelin development and persistent hypomyelination in JOE mice. Overall these non-invasive techniques are capable of spatially resolving the increase in myelination in the normally developing and developmentally delayed mouse brain.

In vivo performance of photovoltaic subretinal prosthesis

NASA Astrophysics Data System (ADS)

Mandel, Yossi; Goetz, George; Lavinsky, Daniel; Huie, Phil; Mathieson, Keith; Wang, Lele; Kamins, Theodore; Manivanh, Richard; Harris, James; Palanker, Daniel

2013-02-01

We have developed a photovoltaic retinal prosthesis, in which camera-captured images are projected onto the retina using pulsed near-IR light. Each pixel in the subretinal implant directly converts pulsed light into local electric current to stimulate the nearby inner retinal neurons. 30 μm-thick implants with pixel sizes of 280, 140 and 70 μm were successfully implanted in the subretinal space of wild type (WT, Long-Evans) and degenerate (Royal College of Surgeons, RCS) rats. Optical Coherence Tomography and fluorescein angiography demonstrated normal retinal thickness and healthy vasculature above the implants upon 6 months follow-up. Stimulation with NIR pulses over the implant elicited robust visual evoked potentials (VEP) at safe irradiance levels. Thresholds increased with decreasing pulse duration and pixel size: with 10 ms pulses it went from 0.5 mW/mm2 on 280 μm pixels to 1.1 mW/mm2 on 140 μm pixels, to 2.1 mW/mm2 on 70 μm pixels. Latency of the implant-evoked VEP was at least 30 ms shorter than in response evoked by the visible light, due to lack of phototransduction. Like with the visible light stimulation in normal sighted animals, amplitude of the implant-induced VEP increased logarithmically with peak irradiance and pulse duration. It decreased with increasing frequency similar to the visible light response in the range of 2 - 10 Hz, but decreased slower than the visible light response at 20 - 40 Hz. Modular design of the photovoltaic arrays allows scalability to a large number of pixels, and combined with the ease of implantation, offers a promising approach to restoration of sight in patients blinded by retinal degenerative diseases.

Evaluation of central nervous system in patients with glycogen storage disease type 1a.

PubMed

Aydemir, Yusuf; Gürakan, Figen; Saltık Temizel, İnci Nur; Demir, Hülya; Oğuz, Kader Karlı; Yalnızoğlu, Dilek; Topçu, Meral; Özen, Hasan; Yüce, Aysel

2016-01-01

We aimed to evaluate structure and functions of central nervous system (CNS) in children with glycogen storage disease (GSD) type 1a. Neurological examination, psychometric tests, electroencephalography (EEG), magnetic resonance imaging (MRI), visual evoked potentials (VEP) and brainstem auditory evoked potentials (BAEP) were performed. The results were compared between patients with good and poor metabolic control and healthy children. Twenty-three patients with GSD type 1a were studied. Twelve patients were in poor metabolic control group and 11 patients in good metabolic control group. Five patients had intellectual disability, 10 had EEG abnormalities, seven had abnormal VEP and two had abnormal BAEP results. MRI was abnormal in five patients. There was significant correlation between the number of hypoglycemic attacks and MRI abnormalities. Central nervous system may be affected in GSD type 1a even in patients with normal neurologic examination. Accumulation of abnormal results in patients with poor metabolic control supports the importance of metabolic control in GSD type 1a.

Effect of extending grating length and width on human visually evoked potentials.

PubMed

Mihaylova, Milena S; Hristov, Ivan; Racheva, Kalina; Totev, Tsvetalin; Mitov, Dimitar

2015-01-01

Visually evoked potentials (VEPs) were elicited by Gabor gratings with different lengths and widths at three spatial frequencies (SFs): low, 1.45 c/deg, medium, 2.9 c/deg and high, 5.8 c/deg and at a contrast 3 times above the detection threshold at each SF. An increase of grating length enhanced N1 amplitude at occipital and parietal positions stronger than the increase of grating width at aspect ratios (length : width) above 4:1. The stronger effect of stimulus length than width was reflected also in the amplitude of the later P1 component at central and parietal positions. The larger effect of stimulus length than width on the VEP amplitude was SF specific: it was stronger at 5.8 c/deg, smaller at 2.9 c/deg and vanished at 1.45 c/deg. The results obtained suggest anisotropy in the physiological mechanisms that underlie grating perception and involve bottom- up processes initiated in the occipital cortex.

Orientation Tuning in the Visual Cortex of 3-Month-old Human Infants

PubMed Central

Baker, Thomas J.; Norcia, Anthony M.; Candy, T. Rowan

2016-01-01

Sensitivity to orientation is critical for making a whole and complete picture of the world. We measured the orientation tuning of mechanisms inthe visual cortex of typically developing 3-month-olds and adults using a nonlinear analysis of the two-input steady-state visually evoked potential (VEP). Two gratings, one a fixed test and the other a variable orientation masker were tagged with distinct temporal frequencies and the corresponding evoked responses were measured at the harmonics of the test and masker frequencies and at a frequency equal to the sum of the two stimulus frequencies. The magnitude of the sum frequency component depended strongly on the relative orientation of the test and masker in both infants and adults. The VEP tuning bandwidths of the 3-month-olds measured at the sum frequency were similar to those of adults, suggesting that behavioral immaturities in functions such as orientation discrimination and contour integration may result from other immaturities in long-range lateral projections or feedback mechanisms. PMID:21236289

Bisensory stimulation increases gamma-responses over multiple cortical regions.

PubMed

Sakowitz, O W; Quiroga, R Q; Schürmann, M; Başar, E

2001-04-01

In the framework of the discussion about gamma (approx. 40 Hz) oscillations as information carriers in the brain, we investigated the relationship between gamma responses in the EEG and intersensory association. Auditory evoked potentials (AEPs) and visual evoked potentials (VEPs) were compared with bisensory evoked potentials (BEPs; simultaneous auditory and visual stimulation) in 15 subjects. Gamma responses in AEPs, VEPs and BEPs were assessed by means of wavelet decomposition. Overall maximum gamma-components post-stimulus were highest in BEPs (P < 0.01). Bisensory evoked gamma-responses also showed significant central, parietal and occipital amplitude-increases (P < 0.001, P < 0.01, P < 0.05, respectively; prestimulus interval as baseline). These were of greater magnitude when compared with the unisensory responses. As a correlate of the marked gamma responses to bimodal stimulation we suggest a process of 'intersensory association', i.e. one of the steps between sensory transmission and perception. Our data may be interpreted as a further example of function-related gamma responses in the EEG.

High infusion pressure in conjunction with vitreous surgery alters the morphology and function of the retina of rabbits.

PubMed

Minami, Masahiro; Oku, Hidehiro; Okuno, Takashi; Fukuhara, Masayuki; Ikeda, Tsunehiko

2007-09-01

To investigate the effects of high infusion pressure in conjunction with pars plana vitrectomy (PPV) on retinal morphology and function in rabbits. Pars plana vitrectomy was performed under urethane (0.8 mg/kg) anaesthesia in the right eye of albino rabbits following phacoemulsification and aspiration (PEA). The left eyes were not touched. After PEA, the animals were divided into two groups. In six eyes, intraocular pressure (IOP) was increased to 80 mmHg for 30 mins (high-pressure group) and in five eyes IOP was maintained at 40 mmHg for 30 mins (low-pressure group). The IOPs were regulated by the height of the bottle of balanced salt solution (BSS) and monitored with a pressure transducer. After the pressure elevation, vitreous fluid was collected to measure the glutamate concentration. Then, PPV was performed for 15 mins in both groups under an infusion pressure of 40 mmHg. In five additional rabbits, PEA alone was performed in the right eye, and vitreous fluid was collected (PEA group). Functional alterations were assessed by recording visual evoked potentials (VEPs) and electroretinograms (ERGs). Ten days after the IOP changes, the animals were killed with intravenous pentobarbital sodium and the eyes were prepared for histological analysis. Damage to retinal ganglion cells (RGCs) was quantified by counting the number of cells in the ganglion cell layer (GCL). The contralateral eyes in the high-pressure group served as controls (n = 6). The mean implicit time (IT) of the VEPs in the high-pressure group was significantly longer than that before the IOP elevation, by 114-124% (p < 0.05, paired t-test), and also than that of control eyes (p < 0.05, anova followed by t-test). No significant changes in the VEPs were detected in either the low-pressure group or the PEA group. There were significantly fewer cells in the GCL in the high-pressure group (24.7/mm) than in the control animals (41.4/mm; p < 0.05, Dunnett's test). The number of cells in the GCL in the low-pressure and PEA groups did not significantly differ to that in the controls. The amplitudes of the ERG a- and b-waves were not significantly changed (p > 0.05, paired t-test). These results suggest that high infusion pressure in conjunction with PPV leads to morphological and functional changes in the retina. The absence of ERG changes and presence of VEP changes suggest that these changes were due to damage to RGCs, which supports the morphological observations.

Nonthermal ablation with microbubble-enhanced focused ultrasound close to the optic tract without affecting nerve function

PubMed Central

McDannold, Nathan; Zhang, Yong-Zhi; Power, Chanikarn; Jolesz, Ferenc; Vykhodtseva, Natalia

2014-01-01

Object Tumors at the skull base are challenging for both resection and radiosurgery given the presence of critical adjacent structures, such as cranial nerves, blood vessels, and brainstem. Magnetic resonance imaging–guided thermal ablation via laser or other methods has been evaluated as a minimally invasive alternative to these techniques in the brain. Focused ultrasound (FUS) offers a noninvasive method of thermal ablation; however, skull heating limits currently available technology to ablation at regions distant from the skull bone. Here, the authors evaluated a method that circumvents this problem by combining the FUS exposures with injected microbubble-based ultrasound contrast agent. These microbubbles concentrate the ultrasound-induced effects on the vasculature, enabling an ablation method that does not cause significant heating of the brain or skull. Methods In 29 rats, a 525-kHz FUS transducer was used to ablate tissue structures at the skull base that were centered on or adjacent to the optic tract or chiasm. Low-intensity, low-duty-cycle ultrasound exposures (sonications) were applied for 5 minutes after intravenous injection of an ultrasound contrast agent (Definity, Lantheus Medical Imaging Inc.). Using histological analysis and visual evoked potential (VEP) measurements, the authors determined whether structural or functional damage was induced in the optic tract or chiasm. Results Overall, while the sonications produced a well-defined lesion in the gray matter targets, the adjacent tract and chiasm had comparatively little or no damage. No significant changes (p > 0.05) were found in the magnitude or latency of the VEP recordings, either immediately after sonication or at later times up to 4 weeks after sonication, and no delayed effects were evident in the histological features of the optic nerve and retina. Conclusions This technique, which selectively targets the intravascular microbubbles, appears to be a promising method of noninvasively producing sharply demarcated lesions in deep brain structures while preserving function in adjacent nerves. Because of low vascularity—and thus a low microbubble concentration—some large white matter tracts appear to have some natural resistance to this type of ablation compared with gray matter. While future work is needed to develop methods of monitoring the procedure and establishing its safety at deep brain targets, the technique does appear to be a potential solution that allows FUS ablation of deep brain targets while sparing adjacent nerve structures. PMID:24010975

[Analysis of 180 patients with sensory defect nystagmus (SDN) and congenital idiopathic nystagmus (CIN)].

PubMed

Lorenz, B; Gampe, E

2001-01-01

Analysis of the diseases underlying congenital nystagmus in a series of patients registered during 6 years as a prerequisite for adequate counselling of the families. Retrospective study of all patients that presented between 1992 and 1998 with congenital nystagmus not related to visual deprivation or acquired pathologies of the visual pathways. The patients were examined clinically and in dependence on the findings also by electrophysiological (Ganzfeld ERG and VEP, Albino-flash-VEP), psychophysical (colour vision, dark adaptation, spectral sensitivity), and molecular genetic methods. When estimated necessary, family members affected by history and unaffected family members were also examined. In cases of complex neuroophthalmological diseases a neuropaediatric examination including neuroimaging was initiated. In total, 180 patients could be analysed. A sensory defect nystagmus (SDN) was present in 142 patients (79%). The diagnoses were as follows: albinism (any form) in 56 patients (30%), progressive photoreceptor dystrophy in 20 patients (11%), stationary cone dysfunction in 18 patients (10%), bilateral optic nerve hypoplasia in 15 patients (8%), chorioretinal or optic nerve colobomata in 10 patients (6%), aniridia and its variants in 10 patients (6%), familial isolated nystagmus in 8 patients (5%), and congenital stationary night blindness in 5 patients (3%). 38 patients (21%) could not (yet) be classified. The prevalence of SDN as the manifesting symptom of a variety of well defined diseases in the present series of at least 79% is similar to that of 90% reported earlier. The precise diagnosis is a prerequisite for counselling the families as to functional prognosis and recurrence risk. Unnecessary neurological examinations including neuroimaging can be avoided.

Searching for biomarkers of CDKL5 disorder: early-onset visual impairment in CDKL5 mutant mice

PubMed Central

Mazziotti, Raffaele; Lupori, Leonardo; Sagona, Giulia; Gennaro, Mariangela; Della Sala, Grazia; Putignano, Elena

2017-01-01

Abstract CDKL5 disorder is a neurodevelopmental disorder still without a cure. Murine models of CDKL5 disorder have been recently generated raising the possibility of preclinical testing of treatments. However, unbiased, quantitative biomarkers of high translational value to monitor brain function are still missing. Moreover, the analysis of treatment is hindered by the challenge of repeatedly and non-invasively testing neuronal function. We analyzed the development of visual responses in a mouse model of CDKL5 disorder to introduce visually evoked responses as a quantitative method to assess cortical circuit function. Cortical visual responses were assessed in CDKL5 null male mice, heterozygous females, and their respective control wild-type littermates by repeated transcranial optical imaging from P27 until P32. No difference between wild-type and mutant mice was present at P25-P26 whereas defective responses appeared from P27-P28 both in heterozygous and homozygous CDKL5 mutant mice. These results were confirmed by visually evoked potentials (VEPs) recorded from the visual cortex of a different cohort. The previously imaged mice were also analyzed at P60–80 using VEPs, revealing a persistent reduction of response amplitude, reduced visual acuity and defective contrast function. The level of adult impairment was significantly correlated with the reduction in visual responses observed during development. Support vector machine showed that multi-dimensional visual assessment can be used to automatically classify mutant and wt mice with high reliability. Thus, monitoring visual responses represents a promising biomarker for preclinical and clinical studies on CDKL5 disorder. PMID:28369421

Visual Cortical Function in Very Low Birth Weight Infants without Retinal or Cerebral Pathology

PubMed Central

Hou, Chuan; Norcia, Anthony M.; Madan, Ashima; Tith, Solina; Agarwal, Rashi

2011-01-01

Purpose. Preterm infants are at high risk of visual and neural developmental deficits. However, the development of visual cortical function in preterm infants with no retinal or neurologic morbidity has not been well defined. To determine whether premature birth itself alters visual cortical function, swept parameter visual evoked potential (sVEP) responses of healthy preterm infants were compared with those of term infants. Methods. Fifty-two term infants and 58 very low birth weight (VLBW) infants without significant retinopathy of prematurity or neurologic morbidities were enrolled. Recruited VLBW infants were between 26 and 33 weeks of gestational age, with birth weights of less than 1500 g. Spatial frequency, contrast, and vernier offset sweep VEP tuning functions were measured at 5 to 7 months' corrected age. Acuity and contrast thresholds were derived by extrapolating the tuning functions to 0 amplitude. These thresholds and suprathreshold response amplitudes were compared between groups. Results. Preterm infants showed increased thresholds (indicating decreased sensitivity to visual stimuli) and reductions in amplitudes for all three measures. These changes in cortical responsiveness were larger in the <30 weeks ' gestational age subgroup than in the ≥30 weeks' gestational age subgroup. Conclusions. Preterm infants with VLBW had measurable and significant changes in cortical responsiveness that were correlated with gestational age. These results suggest that premature birth in the absence of identifiable retinal or neurologic abnormalities has a significant effect on visual cortical sensitivity at 5 to 7 months' of corrected age and that gestational age is an important factor in visual development. PMID:22025567

Nonthermal ablation with microbubble-enhanced focused ultrasound close to the optic tract without affecting nerve function.

PubMed

McDannold, Nathan; Zhang, Yong-Zhi; Power, Chanikarn; Jolesz, Ferenc; Vykhodtseva, Natalia

2013-11-01

Tumors at the skull base are challenging for both resection and radiosurgery given the presence of critical adjacent structures, such as cranial nerves, blood vessels, and brainstem. Magnetic resonance imaging-guided thermal ablation via laser or other methods has been evaluated as a minimally invasive alternative to these techniques in the brain. Focused ultrasound (FUS) offers a noninvasive method of thermal ablation; however, skull heating limits currently available technology to ablation at regions distant from the skull bone. Here, the authors evaluated a method that circumvents this problem by combining the FUS exposures with injected microbubble-based ultrasound contrast agent. These microbubbles concentrate the ultrasound-induced effects on the vasculature, enabling an ablation method that does not cause significant heating of the brain or skull. In 29 rats, a 525-kHz FUS transducer was used to ablate tissue structures at the skull base that were centered on or adjacent to the optic tract or chiasm. Low-intensity, low-duty-cycle ultrasound exposures (sonications) were applied for 5 minutes after intravenous injection of an ultrasound contrast agent (Definity, Lantheus Medical Imaging Inc.). Using histological analysis and visual evoked potential (VEP) measurements, the authors determined whether structural or functional damage was induced in the optic tract or chiasm. Overall, while the sonications produced a well-defined lesion in the gray matter targets, the adjacent tract and chiasm had comparatively little or no damage. No significant changes (p > 0.05) were found in the magnitude or latency of the VEP recordings, either immediately after sonication or at later times up to 4 weeks after sonication, and no delayed effects were evident in the histological features of the optic nerve and retina. This technique, which selectively targets the intravascular microbubbles, appears to be a promising method of noninvasively producing sharply demarcated lesions in deep brain structures while preserving function in adjacent nerves. Because of low vascularity--and thus a low microbubble concentration--some large white matter tracts appear to have some natural resistance to this type of ablation compared with gray matter. While future work is needed to develop methods of monitoring the procedure and establishing its safety at deep brain targets, the technique does appear to be a potential solution that allows FUS ablation of deep brain targets while sparing adjacent nerve structures.

An "oblique effect" in the visual evoked potential of the cat.

PubMed

Bonds, A B

1982-01-01

An oblique effect was observed in the amplitude of the VEP recorded from area 17 of the cat. The ratio of the responses to oblique gratings compared with responses to horizontal and vertical gratings averaged 0.77. Orientation dependence was strongest at low spatial frequencies, unlike the effect found in primates.

Tadpole-shaped lateralized parietal atretic cephalocele associated with an ipsilateral lacrimal gland fistula and schizencephalic clefts.

PubMed

Murakami, Nobuya; Morioka, Takato; Suzuki, Satoshi O; Mukae, Nobutaka; Hashiguchi, Kimiaki; Iihara, Koji

2017-02-01

Parietal atretic cephalocele (AC) and its associated intracranial venous anomalies, such as vertical embryonic positioning of the straight sinus (VEP of SS), have, in previous reports, been exclusively restricted to the midline. We report a patient with lateralized parietal AC on the right side. The AC was in the shape of a tadpole, with a large head and a long tail, extending to the proximity of the right external canthus, where a lacrimal gland fistula was observed. The superior sagittal sinus and VEP of SS were also displaced to the right side, although the sagittal suture was located at the midline. Schizencephalic clefts in the right posterior cortex were also observed. The parietal AC, which was initially located in the midline, could conceivably have been displaced to the right side by other developmental processes. However, the relationship between lateralized AC and associated multiple anomalies on the ipsilateral side is difficult to explain monogenetically. Our case study indicates that AC might have a broader spectrum of clinical symptoms than was once thought to be the case.

Long-Term Regulation of the Local Renin-Angiotensin System in the Myocardium of Spontaneously Hypertensive Rats by Feeding Bioactive Peptides Derived from Spirulina platensis.

PubMed

Pan, Huanglei; She, Xingxing; Wu, Hongli; Ma, Jun; Ren, Difeng; Lu, Jun

2015-09-09

This study investigated the long-term (8 weeks) anti-hypertensive effects of 10 mg/kg tripeptides isolated from Spirulina platensis, Ile-Gln-Pro (IQP) and Val-Glu-Pro (VEP), and S. platensis hydrolysates (SH) on spontaneously hypertensive rats. The treatment period was 6 weeks, and observation continued for another 2 weeks. After treatment, weighted systolic blood pressure, weighted diastolic blood pressure, left ventricular mass index, and right ventricular mass index of groups treated with IQP, VEP, and SH were significantly lower than those of the group treated with distilled water, even when the treatments had been withdrawn for 2 weeks. Quantitative real-time polymerase chain reaction, enzyme-linked immunosorbent assay, and Western blotting showed the mRNA expression levels and protein/peptide concentrations of the main components of the renin angiotensin system in myocardium were significantly affected by treatment: angiotensin converting enzyme, angiotensin II, and angiotensin type 1 receptor were down-regulated, whereas angiotensin type 2 receptor, angiotensin converting enzyme 2, angiotensin-(1-7), and Mas receptor were up-regulated.

Enhanced and bilateralized visual sensory processing in the ventral stream may be a feature of normal aging.

PubMed

De Sanctis, Pierfilippo; Katz, Richard; Wylie, Glenn R; Sehatpour, Pejman; Alexopoulos, George S; Foxe, John J

2008-10-01

Evidence has emerged for age-related amplification of basic sensory processing indexed by early components of the visual evoked potential (VEP). However, since these age-related effects have been incidental to the main focus of these studies, it is unclear whether they are performance dependent or alternately, represent intrinsic sensory processing changes. High-density VEPs were acquired from 19 healthy elderly and 15 young control participants who viewed alphanumeric stimuli in the absence of any active task. The data show both enhanced and delayed neural responses within structures of the ventral visual stream, with reduced hemispheric asymmetry in the elderly that may be indicative of a decline in hemispheric specialization. Additionally, considerably enhanced early frontal cortical activation was observed in the elderly, suggesting frontal hyper-activation. These age-related differences in early sensory processing are discussed in terms of recent proposals that normal aging involves large-scale compensatory reorganization. Our results suggest that such compensatory mechanisms are not restricted to later higher-order cognitive processes but may also be a feature of early sensory-perceptual processes.

Evaluation of visual field parameters in patients with chronic obstructive pulmonary disease.

PubMed

Demir, Helin Deniz; Inönü, Handan; Kurt, Semiha; Doruk, Sibel; Aydın, Erdinc; Etikan, Ilker

2012-08-01

To evaluate the effects of chronic obstructive pulmonary disease (COPD) on retina and optic nerve. Thirty-eight patients with COPD and 29 healthy controls, totally 67 subjects, were included in the study. Visual evoked potentials (VEP) and visual field assessment (both standard achromatic perimetry (SAP) and short-wavelength automated perimetry (SWAP)) were performed on each subject after ophthalmological, neurological and pulmonary examinations. Mean deviation (MD), pattern standard deviation (PSD) and corrected pattern standard deviation (CPSD) were significantly different between patient and control groups as for both SAP and SWAP measurements (p = 0.001, 0.019, 0.009 and p = 0.004,0.019, 0.031, respectively). Short-term fluctuation (SF) was not statistically different between the study and the control groups (p = 0.874 and 0.694, respectively). VEP P100 latencies were significantly different between patients with COPD and the controls (p = 0.019). Chronic obstructive pulmonary disease is a systemic disease, and hypoxia in COPD seems to affect the retina and the optic nerve. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.

Neurotoxic effects of n-hexane on the human central nervous system: evoked potential abnormalities in n-hexane polyneuropathy.

PubMed Central

Chang, Y C

1987-01-01

An outbreak of n-hexane polyneuropathy as a result of industrial exposure occurred in printing factories in Taipei area from December 1983 to February 1985. Multimodality evoked potentials study was performed on 22 of the polyneuropathy cases, five of the subclinical cases, and seven of the unaffected workers. The absolute and interpeak latencies of patterned visual evoked potential (pVEP) in both the polyneuropathy and subclinical groups were longer than in the normal controls. The pVEP interpeak amplitude was also decreased in the polyneuropathy cases. Brainstem auditory evoked potentials (BAEP), showed no difference of wave I latency between factory workers and normal controls, but prolongation of the wave I-V interpeak latencies was noted, corresponding with the severity of the polyneuropathy. In somatosensory evoked potentials (SEPs), both the absolute latencies and central conduction time (CCT) were longer in subclinical and polyneuropathy cases than in the unaffected workers and normal controls. From this evoked potentials study, chronic toxic effects of n-hexane on the central nervous system were shown. PMID:3031221

The hybrid BCI system for movement control by combining motor imagery and moving onset visual evoked potential.

PubMed

Ma, Teng; Li, Hui; Deng, Lili; Yang, Hao; Lv, Xulin; Li, Peiyang; Li, Fali; Zhang, Rui; Liu, Tiejun; Yao, Dezhong; Xu, Peng

2017-04-01

Movement control is an important application for EEG-BCI (EEG-based brain-computer interface) systems. A single-modality BCI cannot provide an efficient and natural control strategy, but a hybrid BCI system that combines two or more different tasks can effectively overcome the drawbacks encountered in single-modality BCI control. In the current paper, we developed a new hybrid BCI system by combining MI (motor imagery) and mVEP (motion-onset visual evoked potential), aiming to realize the more efficient 2D movement control of a cursor. The offline analysis demonstrates that the hybrid BCI system proposed in this paper could evoke the desired MI and mVEP signal features simultaneously, and both are very close to those evoked in the single-modality BCI task. Furthermore, the online 2D movement control experiment reveals that the proposed hybrid BCI system could provide more efficient and natural control commands. The proposed hybrid BCI system is compensative to realize efficient 2D movement control for a practical online system, especially for those situations in which P300 stimuli are not suitable to be applied.

Evaluation of central and peripheral neuropathy in patients with chronic obstructive pulmonary disease.

PubMed

Aras, Yeşim Güzey; Aydemir, Yusuf; Güngen, Belma Doğan; Güngen, Adil Can

2018-01-01

The aim of the study was to investigate the frequency and characteristics of peripheral nervous system (PNS) and central nervous system (CNS) involvement in COPD. The study included 41 COPD patients and 41 healthy volunteers. Electrophysiological studies were carried out: electromyography (EMG) and visual evoked potentials (VEPs). The median nerve, ulnar nerve, common peroneal nerve, and tibial nerve were evaluated for latency, amplitude, and conduction velocity. The mean age of patients with COPD was 61.8 years and disease duration 10.3 years. There was no difference between patient and control groups in terms of age, BMI, smoking status, or biochemical parameters. Upon VEP examination, latencies were significantly prolonged and amplitudes shortened in the patient group compared to the control group. In EMG measurements, conduction velocity and amplitudes in all nerves were low in the patient group. Similarly, latencies in all nerves were higher in patients with COPD. Central and peripheral nervous system involvement could develop in patients with moderate-severe COPD, and these patients should be monitored for neuropathic changes in combination with neurological examination.

WHATIF: an open-source desktop application for extraction and management of the incidental findings from next-generation sequencing variant data

PubMed Central

Ye, Zhan; Kadolph, Christopher; Strenn, Robert; Wall, Daniel; McPherson, Elizabeth; Lin, Simon

2015-01-01

Background Identification and evaluation of incidental findings in patients following whole exome (WGS) or whole genome sequencing (WGS) is challenging for both practicing physicians and researchers. The American College of Medical Genetics and Genomics (ACMG) recently recommended a list of reportable incidental genetic findings. However, no informatics tools are currently available to support evaluation of incidental findings in next-generation sequencing data. Methods The Wisconsin Hierarchical Analysis Tool for Incidental Findings (WHATIF), was developed as a stand-alone Windows-based desktop executable, to support the interactive analysis of incidental findings in the context of the ACMG recommendations. WHATIF integrates the European Bioinformatics Institute Variant Effect Predictor (VEP) tool for biological interpretation and the National Center for Biotechnology Information ClinVar tool for clinical interpretation. Results An open-source desktop program was created to annotate incidental findings and present the results with a user-friendly interface. Further, a meaningful index (WHATIF Index) was devised for each gene to facilitate ranking of the relative importance of the variants and estimate the potential workload associated with further evaluation of the variants. Our WHATIF application is available at: http://tinyurl.com/WHATIF-SOFTWARE Conclusions The WHATIF application offers a user-friendly interface and allows users to investigate the extracted variant information efficiently and intuitively while always accessing the up to date information on variants via application programming interfaces (API) connections. WHATIF’s highly flexible design and straightforward implementation aids users in customizing the source code to meet their own special needs. PMID:25890833

Neuropathies of the optic nerve and visual evoked potentials with special reference to color vision and differential light threshold measured with the computer perimeter OCTOPUS.

PubMed

Wildberger, H

1984-10-31

The contrast evoked potentials (VEPs) to different check sizes were recorded in about 200 cases of discrete optic neuropathies (ON) of different origin. Differential light threshold (DLT) was tested with the computer perimeter OCTOPUS. Saturated and desaturated tests were applied to evaluate the degree of acquired color vision deficiency. Delayed VEP responses are not confined to optic neuritis (RBN) alone and the different latency times obtained from other ON are confluent. The delay may be due to demyelination, to an increasing dominance of paramacular VEP subcomponents or to an increasing dominance of the upper half-field responses. Recording with smaller check sizes has the advantage that discrete dysfunctions in the visual field (VF) center are more easily detected: a correlation between amplitudes and visual acuity is best in strabismic amblyopias, is less expressed in maculopathies of the retina and weak in ON. The absence or reduction of amplitudes to smaller check sizes, however, is an important indication of a disorder in the VF center of ON in an early or recovered stage. Acquired color vision defects of the tritan-like type are more confined to discrete ON, whereas the red/green type is reserved to more severe ON. The DLT of the VF center is reduced in a different, significant and non significant extent in discrete optic neuropathies and the correlation between DLT and visual acuity is weak. A careful numerical analysis is needed in types of discrete ON where the central DLT lies within normal statistical limits: a side difference of the DLT between the affected and the normal fellow eye is always present. Evaluation of visual fatigue effects and of the relative sensitivity loss of VF center and VF periphery may provide further diagnostic information.

Electrophysiological assessment for early detection of retinal dysfunction in β-thalassemia major patients.

PubMed

Dettoraki, Maria; Kattamis, Antonis; Ladas, Ioannis; Maragkos, Konstantinos; Koutsandrea, Chryssanthi; Chatzistefanou, Klio; Laios, Konstantinos; Brouzas, Dimitrios; Moschos, Marilita M

2017-07-01

The purpose of this study was to assess the role of various diagnostic tests in early detection of retinal changes in β-thalassemia major patients. Thirty-eight visually asymptomatic β-thalassemia major patients receiving regular blood transfusions and iron-chelation therapy with deferoxamine (group A, n = 13), deferasirox (group B, n = 11) or deferoxamine with deferiprone (group C, n = 14) and fourteen age- and sex- matched healthy individuals were included in the study. All participants underwent ophthalmoscopy, full-field electroretinography (ERG), visual evoked potentials (VEP), multifocal electroretinography (mfERG), fundus autofluorescence (FAF) imaging and optical coherence tomography (OCT) scans. Retinal pigment epithelium changes were present in two cases. Scotopic ERG demonstrated decreased a-wave amplitude in groups A, B and C (p = 0.03, p = 0.002 and p = 0.002, respectively) and decreased b-wave amplitude in groups B and C (p = 0.002 and p = 0.01, respectively) compared to controls. Photopic ERG showed delayed b-wave latency in groups A and C (p = 0.03 and p = 0.03, respectively) ERG maximal combined response and VEP response did not differ between groups. MfERG showed reduced retinal response density in ring 1 in groups A, B, C (p < 0.001, p < 0.001, p = 0.001, respectively) and ring 2 in group B (p = 0.02) and delayed latency in ring 5 in groups A and B (p = 0.04 and p = 0.04, respectively). Abnormal FAF images appeared in three cases and OCT abnormalities in one case, whereas no changes were observed in controls (p = 0.55 and p = 1.00, respectively). Full-field ERG and mfERG are more sensitive tools for detecting early retinal changes in β-thalassemia patients compared with ophthalmoscopy, VEP, FAF imaging and OCT scans.

Moderate perinatal thyroid hormone insufficiency alters visual system function in adult rats.

PubMed

Boyes, William K; Degn, Laura; George, Barbara Jane; Gilbert, Mary E

2018-04-21

Thyroid hormone (TH) is critical for many aspects of neurodevelopment and can be disrupted by a variety of environmental contaminants. Sensory systems, including audition and vision are vulnerable to TH insufficiencies, but little data are available on visual system development at less than severe levels of TH deprivation. The goal of the current experiments was to explore dose-response relations between graded levels of TH insufficiency during development and the visual function of adult offspring. Pregnant Long Evans rats received 0 or 3 ppm (Experiment 1), or 0, 1, 2, or 3 ppm (Experiment 2) of propylthiouracil (PTU), an inhibitor of thyroid hormone synthesis, in drinking water from gestation day (GD) 6 to postnatal day (PN) 21. Treatment with PTU caused dose-related reductions of serum T4, with recovery on termination of exposure, and euthyroidism by the time of visual function testing. Tests of retinal (electroretinograms; ERGs) and visual cortex (visual evoked potentials; VEPs) function were assessed in adult offspring. Dark-adapted ERG a-waves, reflecting rod photoreceptors, were increased in amplitude by PTU. Light-adapted green flicker ERGs, reflecting M-cone photoreceptors, were reduced by PTU exposure. UV-flicker ERGs, reflecting S-cones, were not altered. Pattern-elicited VEPs were significantly reduced by 2 and 3 ppm PTU across a range of stimulus contrast values. The slope of VEP amplitude-log contrast functions was reduced by PTU, suggesting impaired visual contrast gain. Visual contrast gain primarily reflects function of visual cortex, and is responsible for adjusting sensitivity of perceptual mechanisms in response to changing visual scenes. The results indicate that moderate levels of pre-and post-natal TH insufficiency led to alterations in visual function of adult rats, including both retinal and visual cortex sites of dysfunction. Copyright © 2018. Published by Elsevier B.V.

Safety and effectiveness of Thulium VapoEnucleation of the prostate (ThuVEP) in patients on anticoagulant therapy.

PubMed

Netsch, Christopher; Stoehrer, M; Brüning, M; Gabuev, A; Bach, T; Herrmann, T R W; Gross, A J

2014-02-01

To evaluate the safety and efficacy of Thulium VapoEnucleation of the prostate (ThuVEP) for patients on oral anticoagulants (OA) with symptomatic benign prostatic obstruction (BPO). Fifty-six patients, undergoing ThuVEP at two institutions, were evaluated from May 2009 until June 2011. All patients were at high cardiopulmonary risk and presented with a median American Society of Anesthesiology score of 3 [interquartile range (IQR) 2-3]. Thirty-two patients were on aspirin, 8 were on clopidogrel or clopidogrel and aspirin, and 16 on phenprocoumon at the time of surgery. Patient demographic, perioperative, and follow-up data were analyzed. Median prostate volume was 50 (IQR 34-76) cc, and resected tissue weight was 32 (IQR 20-50) g. The median operative time was 61.5 (IQR 40-100.75) min, and the catheter time 2 (IQR 2-3) days. There were no perioperative thromboembolic events. Five patients (8.9%) required a second-look operation in the immediate postoperative course (hemorrhage n = 4, residual adenoma n = 1) and four (7.1%) blood transfusions. Complications within the first 30 days included urinary tract infections (1.7%), urinary retention (3.6%), and delayed bleeding (7.1%). These complications were managed conservatively. At 12-month follow-up, median QoL [5 (IQR 3.75-5) vs. 1 (IQR 1-2)], IPSS [21.5 (IQR 15.5-23.75) vs. 5 (IQR 3-8)], Qmax [7.7 (IQR 6.3-10) vs. 28.3 (IQR 21.25-39.2) ml/s], and postvoiding residual urine [100 (IQR 46-200) vs. 17.5 (IQR 0-36) ml] improved significantly (p < 0.002). Thulium VapoEnucleation of the prostate seems to be a safe and efficacious procedure for the treatment of symptomatic BPO in patients at high cardiopulmonary risk on OA.

Treating amblyopia in adults with prosthetic occluding contact lenses.

PubMed

Garcia-Romo, Esperanza; Perez-Rico, Consuelo; Roldán-Díaz, Isabel; Arévalo-Serrano, Juan; Blanco, Román

2018-05-01

To investigate the feasibility, effectiveness and acceptability of using prosthetic occluding contact lenses (OCLs) to treat moderate amblyopia in adults and of the role of the multifocal visual evoked potential (mfVEP) as a predictor of postamblyopic therapy. A comparative, prospective, interventional, case series pilot study with amblyopic adults (mean age: 40 years, range 20-50 years) allocated into two intervention groups: eye patching and OCL. The primary outcome variable was logarithm of the minimum angle of resolution (logMAR) best-corrected visual acuity (BCVA), and secondary outcomes were mfVEP amplitude and latency and patients' health-related quality of life National Eye Institute Visual Function Questionnaire (NEI VFQ-25). Significant improvements in pre- to postamblyopic therapy BCVA were seen at 1.5 months in the OCL group [0.29 logMAR, 95% confidence interval (CI): 0.10-0.47 versus 0.11 logMAR, 95% CI: 0.02-0.19; p < 0.001] and eye patching group (0.29 logMAR, 95% CI: 0.17-0.40 versus 0.18 logMAR, 95% CI: 0.12-0.23; p < 0.01). Post-treatment BCVA was inversely related to age (R: 0.009, 95% CI: -0.02 to -0.001; p = 0.04) and the presence of strabismus (R: -0.3, 95% CI: -0.434 to -0.17; p = 0.001). No significant changes in the number and size of the abnormal mfVEP amplitude and latency defects were observed after occlusion. The NEI VFQ-25 composite score showed significant improvement in the OCL users at 12 months compared to eye patching. Significant vision improvement can be achieved, making occlusion with OCLs an effective and more acceptable therapy for adults with amblyopia. © 2017 Acta Ophthalmologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

The Time Course of Segmentation and Cue-Selectivity in the Human Visual Cortex

PubMed Central

Appelbaum, Lawrence G.; Ales, Justin M.; Norcia, Anthony M.

2012-01-01

Texture discontinuities are a fundamental cue by which the visual system segments objects from their background. The neural mechanisms supporting texture-based segmentation are therefore critical to visual perception and cognition. In the present experiment we employ an EEG source-imaging approach in order to study the time course of texture-based segmentation in the human brain. Visual Evoked Potentials were recorded to four types of stimuli in which periodic temporal modulation of a central 3° figure region could either support figure-ground segmentation, or have identical local texture modulations but not produce changes in global image segmentation. The image discontinuities were defined either by orientation or phase differences across image regions. Evoked responses to these four stimuli were analyzed both at the scalp and on the cortical surface in retinotopic and functional regions-of-interest (ROIs) defined separately using fMRI on a subject-by-subject basis. Texture segmentation (tsVEP: segmenting versus non-segmenting) and cue-specific (csVEP: orientation versus phase) responses exhibited distinctive patterns of activity. Alternations between uniform and segmented images produced highly asymmetric responses that were larger after transitions from the uniform to the segmented state. Texture modulations that signaled the appearance of a figure evoked a pattern of increased activity starting at ∼143 ms that was larger in V1 and LOC ROIs, relative to identical modulations that didn't signal figure-ground segmentation. This segmentation-related activity occurred after an initial response phase that did not depend on the global segmentation structure of the image. The two cue types evoked similar tsVEPs up to 230 ms when they differed in the V4 and LOC ROIs. The evolution of the response proceeded largely in the feed-forward direction, with only weak evidence for feedback-related activity. PMID:22479566

Effects of toothbrush hardness on in vitro wear and roughness of composite resins.

PubMed

Kyoizumi, Hideaki; Yamada, Junji; Suzuki, Toshimitsu; Kanehira, Masafumi; Finger, Werner J; Sasaki, Keiichi

2013-11-01

To investigate and compare the effects of toothbrushes with different hardness on abrasion and surface roughness of composite resins. Toothbrushes (DENT. EX Slimhead II 33, Lion Dental Products Co. Ltd., Tokyo, Japan) marked as soft, medium and hard, were used to brush 10 beam-shaped specimens of each of three composites resins (Venus [VEN], Venus Diamond [VED] and Venus Pearl [VEP]; HeraeusKulzer) with standardized calcium carbonate slurry in a multistation testing machine (2N load, 60 Hz). After each of five cycles with 10k brushing strokes the wear depth and surface roughness of the specimens were determined. After completion of 50k strokes representative samples were inspected by SEM. Data were treated with ANOVA and regression analyses (p < 0.05). Abrasion of the composite resins increased linearly with increasing number of brushing cycles (r² > 0.9). Highest wear was recorded for VEN, lowest for VED. Hard brushes produced significantly higher wear on VEN and VEP, whereas no difference in wear by toothbrush type was detected for VED. Significantly highest surface roughness was found on VED specimens (Ra > 1.5 µm), the lowest one on VEN (Ra < 0.3 µm). VEN specimens showed increased numbers of pinhole defects when brushed with hard toothbrushes, surfaces of VEP were uniformly abraded without level differences between the prepolymerized fillers and the glass filler-loaded matrix, VED showed large glass fillers protruding over the main filler-loaded matrix portion under each condition. Abrasion and surface roughness of composite resins produced by toothbrushing with dentifrice depend mainly on the type of restorative resin. Hardness grades of toothbrushes have minor effects only on abrasion and surface roughness of composite resins. No relationship was found between abrasion and surface roughness. The grade of the toothbrush used has minor effect on wear, texture and roughness of the composite resin.

Haemodilution and head-down tilting induce functional injury in the rat optic nerve: A model for peri-operative ischemic optic neuropathy.

PubMed

Roth, Steven; Dreixler, John; Newman, Nancy J

2018-05-15

Mechanisms of peri-operative ischaemic optic neuropathy remain poorly understood. Both specific pre-operative and intra-operative factors have been examined by retrospective studies, but no animal model currently exists. To develop a rodent model of peri-operative ischaemic optic neuropathy. In rats, we performed head-down tilt and/or haemodilution, theorising that the combination damages the optic nerve. Animal study. Laboratory. A total of 36 rats, in four groups, completed the functional examination of retina and optic nerve after the interventions. Anaesthetised groups (n>8) were supine (SUP) for 5 h, head-down tilted 70° for 5 h, head-down tilted/haemodiluted for 5 h or SUP/haemodiluted for 5 h. We measured blood pressure, heart rate, intra-ocular pressure and maintained constant temperature. Retinal function (electroretinography), scotopic threshold response (STR) (for retinal ganglion cells) and visual evoked potentials (VEP) (for transmission through the optic nerve). We imaged the optic nerve in vivo and evaluated retinal histology, apoptotic cells and glial activation in the optic nerve. Retinal and optic nerve function were followed to 14 and 28 days after experiments. At 28 days in head down tilted/haemodiluted rats, negative STR decreased (about 50% amplitude reduction, P = 0.006), VEP wave N2-P3 decreased (70% amplitude reduction, P = 0.01) and P2 latency increased (35%, P = 0.003), optic discs were swollen and glial activation was present in the optic nerve. SUP/haemodiluted rats had decreases in negative STR and increased VEP latency, but no glial activation. An injury partly resembling human ischaemic optic neuropathy can be produced in rats by combining haemodilution and head-down tilt. Significant functional changes were also present with haemodilution alone. Future studies with this partial optic nerve injury may enable understanding of mechanisms of peri-operative ischaemic optic neuropathy and could help discover preventive or treatment strategies.

Searching for biomarkers of CDKL5 disorder: early-onset visual impairment in CDKL5 mutant mice.

PubMed

Mazziotti, Raffaele; Lupori, Leonardo; Sagona, Giulia; Gennaro, Mariangela; Della Sala, Grazia; Putignano, Elena; Pizzorusso, Tommaso

2017-06-15

CDKL5 disorder is a neurodevelopmental disorder still without a cure. Murine models of CDKL5 disorder have been recently generated raising the possibility of preclinical testing of treatments. However, unbiased, quantitative biomarkers of high translational value to monitor brain function are still missing. Moreover, the analysis of treatment is hindered by the challenge of repeatedly and non-invasively testing neuronal function. We analyzed the development of visual responses in a mouse model of CDKL5 disorder to introduce visually evoked responses as a quantitative method to assess cortical circuit function. Cortical visual responses were assessed in CDKL5 null male mice, heterozygous females, and their respective control wild-type littermates by repeated transcranial optical imaging from P27 until P32. No difference between wild-type and mutant mice was present at P25-P26 whereas defective responses appeared from P27-P28 both in heterozygous and homozygous CDKL5 mutant mice. These results were confirmed by visually evoked potentials (VEPs) recorded from the visual cortex of a different cohort. The previously imaged mice were also analyzed at P60-80 using VEPs, revealing a persistent reduction of response amplitude, reduced visual acuity and defective contrast function. The level of adult impairment was significantly correlated with the reduction in visual responses observed during development. Support vector machine showed that multi-dimensional visual assessment can be used to automatically classify mutant and wt mice with high reliability. Thus, monitoring visual responses represents a promising biomarker for preclinical and clinical studies on CDKL5 disorder. © The Author 2017. Published by Oxford University Press.

Prediction of long-term disability in multiple sclerosis.

PubMed

Schlaeger, R; D'Souza, M; Schindler, C; Grize, L; Dellas, S; Radue, E W; Kappos, L; Fuhr, P

2012-01-01

Little is known about the predictive value of neurophysiological measures for the long-term course of multiple sclerosis (MS). To prospectively investigate whether combined visual (VEP) and motor evoked potentials (MEP) allow prediction of disability over 14 years. A total of 30 patients with relapsing-remitting and secondary progressive MS were prospectively investigated with VEPs, MEPs and the Expanded Disability Status Scale (EDSS) at entry (T0) and after 6, 12 and 24 months, and with cranial MRI scans at entry (T2-weighted and gadolinium-enhanced T1-weighted images). EDSS was again assessed at year 14 (T4). The association between evoked potential (EP), magnetic resonance (MR) data and EDSS was measured using Spearman's rank correlation. Multivariable linear regression was performed to predict EDSS(T4) as a function of z-transformed EP-latencies(T0). The model was validated using a jack-knife procedure and the potential for improving it by inclusion of additional baseline variables was examined. EDSS values(T4) correlated with the sum of z-transformed EP-latencies(T0) (rho = 0.68, p < 0.0001), but not with MR-parameters(T0). EDSS(T4) as predicted by the formula EDSS(T4) = 4.194 + 0.088 * z-score P100(T0) + 0.071 * z-score CMCT(UE, T0) correlated with the observed values (rho = 0.69, p < 0.0001). Combined EPs allow prediction of long-term disability in small groups of patients with MS. This may have implications for the choice of monitoring methods in clinical trials and for daily practice decisions.

A Comparison of Functional and Structural Measures for Identifying Progression of Glaucoma

PubMed Central

Xin, Daiyan; Greenstein, Vivienne C.; Ritch, Robert; Liebmann, Jeffrey M.; De Moraes, Carlos Gustavo

2011-01-01

Purpose. To compare glaucoma progression by functional and structural tests. Methods. The authors prospectively studied 33 glaucoma patients (55 eyes); 20 eyes (15 patients) had disc hemorrhage, and 35 eyes (18 patients) had exfoliation glaucoma. The following tests were performed at two baseline and three follow-up examinations: frequency doubling perimetry (FDT), 24-2 Humphrey visual fields (HVF), multifocal visual evoked potentials (mfVEP), and optical coherence tomography (OCT). To identify progression, the baseline measurements were averaged and compared to those obtained at the final examination. Stereophotographs of the optic disc were obtained at baseline and compared with those at the final examination. Results. Patients were followed up for 21.1 ± 1.8 months. For HVF there were significant changes in mean deviation (MD) in eight (14.5%) eyes but in pattern standard deviation (P/SD) in only two (3.6%) eyes. For FDT, there were significant changes in MD in 13 (23.6%) eyes. Five eyes showed changes in MD for HVF and FDT. For mfVEP, there was an increase in abnormal points in nine (16.4%) eyes. Six of these eyes did not show significant HVF or FDT changes. For OCT, RNFL average thickness values were significantly decreased in nine (16.4%) eyes. Nine (16.4%) eyes showed progression on stereophotography; four of these eyes did not show significant changes on OCT and functional tests. Conclusions. Each test showed evidence of progression in some eyes. However, agreement among tests and stereophotography regarding which eyes showed progression was poor, illustrating the importance of following up patients with a combination of functional and structural tests. PMID:20847115

Cortical visual evoked potentials recorded after optic tract near field stimulation during GPi-DBS in non-cooperative patients.

PubMed

Landi, Andrea; Pirillo, David; Cilia, Roberto; Antonini, Angelo; Sganzerla, Erik P

2011-02-01

Neurophysiologic monitoring during deep brain stimulation (DBS) interventions in the globus pallidus internum (Gpi) for the treatment of Parkinson's disease or primary dystonia is generally based upon microelectrode recordings (MER); moreover, MER request sophisticated technology and high level trained personnel for a reliable monitoring. Recordings of cortical visual evoked potentials (CVEPs) obtained after stimulation of the optic tract may be a potential option to MER; since optic tract lies just beneath the best target for Gpi DBS, changes in CVEPs during intraoperative exploration may drive a correct electrode positioning. Cortical VEPs from optic tract stimulation (OT C-CEPs) have been recorded in seven patients during GPi-DBS for the treatment of Parkinson's disease and primary dystonia under general sedation. OT C-VEPs were obtained after near-field monopolar stimulation of the optic tract; recording electrodes were at the scalp. Cortical responses after optic tract versus standard visual stimulation were compared. After intraoperative near-field OT stimulation a biphasic wave, named N40-P70, was detected in all cases. N40-P70 neither change in morphology nor in latency at different depths, but increased in amplitude approaching the optic tract. The electrode tip was positioned just 1mm above the point where OT-CVEPs showed the larger amplitude. No MERs were obtained in these patients; OT CVEPs were the only method to detect the Gpi before positioning the electrodes. OT CVEPs seem to be as reliable as MER to detail the optimal target in Gpi surgery: in addition they are less expensive, faster to perform and easier to decode. Copyright © 2010. Published by Elsevier B.V.

Altered Automatic Face Processing in Individuals with High-Functioning Autism Spectrum Disorders: Evidence from Visual Evoked Potentials

ERIC Educational Resources Information Center

Fujita, Takako; Kamio, Yoko; Yamasaki, Takao; Yasumoto, Sawa; Hirose, Shinichi; Tobimatsu, Shozo

2013-01-01

Individuals with autism spectrum disorders (ASDs) have different automatic responses to faces than typically developing (TD) individuals. We recorded visual evoked potentials (VEPs) in 10 individuals with high-functioning ASD (HFASD) and 10 TD individuals. Visual stimuli consisted of upright and inverted faces (fearful and neutral) and objects…

Brief Report: Early VEPs to Pattern-Reversal in Adolescents and Adults with Autism

ERIC Educational Resources Information Center

Kovarski, K.; Thillay, A.; Houy-Durand, E.; Roux, S.; Bidet-Caulet, A.; Bonnet-Brilhault, F.; Batty, M.

2016-01-01

Autism spectrum disorder (ASD) is characterized by atypical visual perception both in the social and nonsocial domain. In order to measure a reliable visual response, visual evoked potentials were recorded during a passive pattern-reversal stimulation in adolescents and adults with and without ASD. While the present results show the same…

Microstructural correlates of infant functional development: example of the visual pathways.

PubMed

Dubois, Jessica; Dehaene-Lambertz, Ghislaine; Soarès, Catherine; Cointepas, Yann; Le Bihan, Denis; Hertz-Pannier, Lucie

2008-02-20

The development of cognitive functions during childhood relies on several neuroanatomical maturation processes. Among these processes is myelination of the white matter pathways, which speeds up electrical conduction. Quantitative indices of such structural processes can be obtained in vivo with diffusion tensor imaging (DTI), but their physiological significance remains uncertain. Here, we investigated the microstructural correlates of early functional development by combining DTI and visual event-related potentials (VEPs) in 15 one- to 4-month-old healthy infants. Interindividual variations of the apparent conduction speed, computed from the latency of the first positive VEP wave (P1), were significantly correlated with the infants' age and DTI indices measured in the optic radiations. This demonstrates that fractional anisotropy and transverse diffusivity are structural markers of functionally efficient myelination. Moreover, these indices computed along the optic radiations showed an early wave of maturation in the anterior region, with the posterior region catching up later in development, which suggests two asynchronous fronts of myelination in both the geniculocortical and corticogeniculate fibers. Thus, in addition to microstructural information, DTI provides noninvasive exquisite information on the functional development of the brain in human infants.

The hybrid BCI system for movement control by combining motor imagery and moving onset visual evoked potential

NASA Astrophysics Data System (ADS)

Ma, Teng; Li, Hui; Deng, Lili; Yang, Hao; Lv, Xulin; Li, Peiyang; Li, Fali; Zhang, Rui; Liu, Tiejun; Yao, Dezhong; Xu, Peng

2017-04-01

Objective. Movement control is an important application for EEG-BCI (EEG-based brain-computer interface) systems. A single-modality BCI cannot provide an efficient and natural control strategy, but a hybrid BCI system that combines two or more different tasks can effectively overcome the drawbacks encountered in single-modality BCI control. Approach. In the current paper, we developed a new hybrid BCI system by combining MI (motor imagery) and mVEP (motion-onset visual evoked potential), aiming to realize the more efficient 2D movement control of a cursor. Main result. The offline analysis demonstrates that the hybrid BCI system proposed in this paper could evoke the desired MI and mVEP signal features simultaneously, and both are very close to those evoked in the single-modality BCI task. Furthermore, the online 2D movement control experiment reveals that the proposed hybrid BCI system could provide more efficient and natural control commands. Significance. The proposed hybrid BCI system is compensative to realize efficient 2D movement control for a practical online system, especially for those situations in which P300 stimuli are not suitable to be applied.

Toluene Inhalation Exposure for 13 Weeks Causes Persistent Changes in Electroretinograms of Long-Evans Rats

PubMed Central

Boyes, William K.; Bercegeay, Mark; Degn, Laura; Beasley, Tracey E.; Evansky, Paul A.; Mwanza, Jean Claude; Geller, Andrew M.; Pinckney, Charles; Nork, T. Michael; Bushnell, Philip J.

2016-01-01

Studies of humans chronically exposed to volatile organic solvents have reported impaired visual functions, including low contrast sensitivity and reduced color discrimination. These reports, however, lacked confirmation from controlled laboratory experiments. To address this question experimentally, we examined visual function by recording visual evoked potentials (VEP) and/or electroretinograms (ERG) from four sets of rats exposed repeatedly to toluene. In addition, eyes of the rats were examined with an ophthalmoscope and some of the retinal tissues were evaluated for rod and M-cone photoreceptor immunohistochemistry. The first study examined rats following exposure to 0, 10, 100 or 1000 ppm toluene by inhalation (6 hr/d, 5 d/wk) for 13 weeks. One week after the termination of exposure, the rats were implanted with chronically indwelling electrodes and the following week pattern-elicited VEPs were recorded. VEP amplitudes were not significantly changed by toluene exposure. Four to five weeks after completion of exposure, rats were dark-adapted overnight, anesthetized, and several sets of electroretinograms (ERG) were recorded. In dark-adapted ERGs recorded over a 5-log (cd-s/m2) range of flash luminance, b-wave amplitudes were significantly reduced at high stimulus luminance values in rats previously exposed to 1000 ppm toluene. A second set of rats, exposed concurrently with the first set, was tested approximately one year after the termination of 13 weeks of exposure to toluene. Again, dark-adapted ERG b-wave amplitudes were reduced at high stimulus luminance values in rats previously exposed to 1000 ppm toluene. A third set of rats was exposed to the same concentrations of toluene for only 4 weeks, and a fourth set of rats exposed to 0 or 1000 ppm toluene for 4 weeks were tested approximately 1 year after the completion of exposure. No statistically significant reductions of ERG b-wave amplitude were observed in either set of rats exposed for 4 weeks. No significant changes were observed in ERG a-wave amplitude or latency, b-wave latency, UV- or green-flicker ERGs, or in photopic flash ERGs. There were no changes in the density of rod or M-cone photoreceptors. The ERG b-wave reflects the firing patterns of on-bipolar cells. The reductions of b-wave amplitude after 13 weeks of exposure and persisting for 1 year suggest that alterations may have occurred in the inner nuclear layer of the retina, where the bipolar cells reside, or the outer or inner plexiform layers where the bipolar cells make synaptic connections. These data provide experimental evidence that repeated exposure to toluene may lead to subtle persistent changes in visual function. The fact that toluene affected ERGs, but not VEPs, suggests that elements in the rat retina may be more sensitive to organic solvent exposure than the rat visual cortex. PMID:26899397

Magnetic iron oxides in the cementation technology of the boron-containing radioactive waste

NASA Astrophysics Data System (ADS)

Fedotov, M. A.; Gorbunova, O. A.; Fedorova, O. V.; Folmanis, G. E.; Kovalenko, L. V.

2015-04-01

Two ways of synthesis of non-detachable dispersed particles of magnetic materials useful for the boron-containing waste cementation process regulation were developed. Powder XRD showed that the method of carbothermic recovery of nanoscale iron hydroxide allows obtaining a mixture of iron oxides with content of the magnetic phase up to 70%. Method of low-temperature hydrogen reduction of the raw materials allows obtaining various compositions of a-iron and iron oxides with the possibility to change the size of the final particles in a wide range. The possibility of using composites of magnetic iron oxides and metal oxide compositions instead of ferromagnetic rods with VEP of boron-containing liquid radioactive waste in the fluidized field was studied. It was shown that the use of fine and nano particles of the iron oxides in the pre-treatment of the boron-containing LRW increases the strength of the final compounds and accelerates the cement setting compounds from 13 to 5-9 days.

Practical Designs of Brain-Computer Interfaces Based on the Modulation of EEG Rhythms

NASA Astrophysics Data System (ADS)

Wang, Yijun; Gao, Xiaorong; Hong, Bo; Gao, Shangkai

A brain-computer interface (BCI) is a communication channel which does not depend on the brain's normal output pathways of peripheral nerves and muscles [1-3]. It supplies paralyzed patients with a new approach to communicate with the environment. Among various brain monitoring methods employed in current BCI research, electroencephalogram (EEG) is the main interest due to its advantages of low cost, convenient operation and non-invasiveness. In present-day EEG-based BCIs, the following signals have been paid much attention: visual evoked potential (VEP), sensorimotor mu/beta rhythms, P300 evoked potential, slow cortical potential (SCP), and movement-related cortical potential (MRCP). Details about these signals can be found in chapter "Brain Signals for Brain-Computer Interfaces". These systems offer some practical solutions (e.g., cursor movement and word processing) for patients with motor disabilities.

Identification and characterization of a type III secretion-associated chaperone in the type III secretion system 1 of Vibrio parahaemolyticus.

PubMed

Akeda, Yukihiro; Okayama, Kanna; Kimura, Tomomi; Dryselius, Rikard; Kodama, Toshio; Oishi, Kazunori; Iida, Tetsuya; Honda, Takeshi

2009-07-01

Vibrio parahaemolyticus causes human gastroenteritis. Genomic sequencing of this organism has revealed that it has two sets of type III secretion systems, T3SS1 and T3SS2, both of which are important for its pathogenicity. However, the mechanism of protein secretion via T3SSs is unknown. A characteristic of many effectors is that they require specific chaperones for efficient delivery via T3SSs; however, no chaperone has been experimentally identified in the T3SSs of V. parahaemolyticus. In this study, we identified candidate T3SS1-associated chaperones from genomic sequence data and examined their roles in effector secretion/translocation and binding to their cognate substrates. From these experiments, we concluded that there is a T3S-associated chaperone, VecA, for a cytotoxic T3SS1-dependent effector, VepA. Further analysis using pulldown and secretion assays characterized the chaperone-binding domain encompassing the first 30-100 amino acids and an amino terminal secretion signal encompassing the first 5-20 amino acids on VepA. These findings will provide a strategy to clarify how the T3SS1 of V. parahaemolyticus secretes its specific effectors.

Connectopathy in Autism Spectrum Disorders: A Review of Evidence from Visual Evoked Potentials and Diffusion Magnetic Resonance Imaging

PubMed Central

Yamasaki, Takao; Maekawa, Toshihiko; Fujita, Takako; Tobimatsu, Shozo

2017-01-01

Individuals with autism spectrum disorder (ASD) show superior performance in processing fine details; however, they often exhibit impairments of gestalt face, global motion perception, and visual attention as well as core social deficits. Increasing evidence has suggested that social deficits in ASD arise from abnormal functional and structural connectivities between and within distributed cortical networks that are recruited during social information processing. Because the human visual system is characterized by a set of parallel, hierarchical, multistage network systems, we hypothesized that the altered connectivity of visual networks contributes to social cognition impairment in ASD. In the present review, we focused on studies of altered connectivity of visual and attention networks in ASD using visual evoked potentials (VEPs), event-related potentials (ERPs), and diffusion tensor imaging (DTI). A series of VEP, ERP, and DTI studies conducted in our laboratory have demonstrated complex alterations (impairment and enhancement) of visual and attention networks in ASD. Recent data have suggested that the atypical visual perception observed in ASD is caused by altered connectivity within parallel visual pathways and attention networks, thereby contributing to the impaired social communication observed in ASD. Therefore, we conclude that the underlying pathophysiological mechanism of ASD constitutes a “connectopathy.” PMID:29170625

Neurosteroid allopregnanolone reduces ipsilateral visual cortex potentiation following unilateral optic nerve injury.

PubMed

Sergeeva, Elena G; Espinosa-Garcia, Claudia; Atif, Fahim; Pardue, Machelle T; Stein, Donald G

2018-05-02

In adult mice with unilateral optic nerve crush injury (ONC), we studied visual response plasticity in the visual cortex following stimulation with sinusoidal grating. We examined visually evoked potentials (VEP) in the primary visual cortex ipsilateral and contralateral to the crushed nerve. We found that unilateral ONC induces enhancement of visual response on the side ipsilateral to the injury that is evoked by visual stimulation to the intact eye. This enhancement was associated with supranormal spatial frequency thresholds in the intact eye when tested using optomotor response. To probe whether injury-induced disinhibition caused the potentiation, we treated animals with the neurosteroid allopregnanolone, a potent agonist of the GABA A receptor, one hour after crush and on post-injury days 3, 8, 13, and 18. Allopregnanolone diminished enhancement of the VEP and this effect was associated with the upregulated synthesis of the δ-subunit of the GABA A receptor. Our study shows a new aspect of experience-dependent plasticity following unilateral ONC. This hyper-activity in the ipsilateral visual cortex is prevented by upregulation of GABA inhibition with allopregnanolone. Our findings suggest the therapeutic potential of allopregnanolone for modulation of plasticity in certain eye and brain disorders and a possible role for disinhibition in ipsilateral hyper-activity following unilateral ONC. Copyright © 2018. Published by Elsevier Inc.

Evaluation of afferent pain pathways in adrenomyeloneuropathic patients.

PubMed

Yagüe, Sara; Veciana, Misericordia; Casasnovas, Carlos; Ruiz, Montserrat; Pedro, Jordi; Valls-Solé, Josep; Pujol, Aurora

2018-03-01

Patients with adrenomyeloneuropathy may have dysfunctions of visual, auditory, motor and somatosensory pathways. We thought on examining the nociceptive pathways by means of laser evoked potentials (LEPs), to obtain additional information on the pathophysiology of this condition. In 13 adrenomyeloneuropathic patients we examined LEPs to leg, arm and face stimulation. Normative data were obtained from 10 healthy subjects examined in the same experimental conditions. We also examined brainstem auditory evoked potentials (BAEPs), pattern reversal full-field visual evoked potentials (VEPs), motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs). Upper and lower limb MEPs and SEPs, as well as BAEPs, were abnormal in all patients, while VEPs were abnormal in 3 of them (23.1%). LEPs revealed abnormalities to stimulation of the face in 4 patients (30.7%), the forearm in 4 patients (30.7%) and the leg in 10 patients (76.9%). The pathologic process of adrenomyeloneuropathy is characterized by a preferential involvement of auditory, motor and somatosensory tracts and less severely of the visual and nociceptive pathways. This non-inflammatory distal axonopathy preferably damages large myelinated spinal tracts but there is also partial involvement of small myelinated fibres. LEPs studies can provide relevant information about afferent pain pathways involvement in adrenomyeloneuropathic patients. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Multimodal recording of brain activity in term newborns during photic stimulation by near-infrared spectroscopy and electroencephalography

NASA Astrophysics Data System (ADS)

Biallas, Martin; Trajkovic, Ivo; Hagmann, Cornelia; Scholkmann, Felix; Jenny, Carmen; Holper, Lisa; Beck, Andreas; Wolf, Martin

2012-08-01

In this study 14 healthy term newborns (postnatal mean age 2.1 days) underwent photic stimulation during sleep on two different days. Near-infrared spectroscopy (NIRS) and electroencephalography (EEG) was acquired simultaneously. The aims of the study were: to determine (i) the sensitivity and (ii) the repeatability of NIRS to detect the hemodynamic response, (iii) the sensitivity and (iv) the repeatability of EEG to detect a visual evoked potential (VEP), (v) to analyze optical data for the optical neuronal signal, and (vi) to test whether inadequate stimulation could be reason for absent hemodynamic responses. The results of the study were as follows. (i) Sensitivity of NIRS was 61.5% to detect hemodynamic responses; (ii) their reproducibility was 41.7%. A VEP was detected (iii) in 96.3% of all subjects with (iv) a reproducibility of 92.3%. (v) In two measurements data met the criteria for an optical neuronal signal. The noise level was 9.6.10-5% change in optical density. (vi) Insufficient stimulation was excluded as reason for absent hemodynamic responses. We conclude that NIRS is an promising tool to study cognitive activation and development of the brain. For clinical application, however, the sensitivity and reproducibility on an individual level needs to be improved.

Sequential involvement of the nervous system in subacute combined degeneration.

PubMed

Minn, Yang-Ki; Kim, Seung-Min; Kim, Se-Hoon; Kwon, Ki-Han; Sunwoo, Il-Nam

2012-03-01

Subacute combined degeneration (SCD) involves progressive degeneration of the spinal cord, optic nerve, and peripheral nerves. Vitamin B12 (VB12) is a co-factor in myelin synthesis. Because each cell that constitutes the myelin component in the central nervous system and peripheral nervous system is different, it is improbable that these cells undergo simultaneous degeneration. However, the sequence of degeneration in SCD has not been established. In this study, we analysed medical records and electrophysiological data of patients who showed neurological symptoms and whose serum VB12 levels were lower than 200 pg/mL. We enrolled 49 patients in this study. Their mean VB12 level was 68.3 pg/mL. Somatosensory evoked potential (SEP) study showed abnormal findings in 38 patients. Of the 40 patients who underwent visual evoked potential (VEP) study, 14 showed abnormal responses. Eighteen patients showed abnormal findings on a nerve conduction study (NCS). In this study, abnormal posterior tibial nerve SEPs only were seen in 16 patients, median nerve SEPs only were seen in 3 patients, abnormal VEPs only in two, and abnormal NCS responses in one patient. No patient complained of cognitive symptoms. In SCD, degeneration appears to progress in the following order: lower spinal cord, cervical spinal cord, peripheral nerve/optic nerve, and finally, the brain.

Screening for Electrophysiological Abnormalities in Chronic Hepatitis C Infection: Peripheral Neuropathy and Optic Neuropathy

PubMed Central

KÖŞKDERELİOĞLU, Aslı; ORTAN, Pınar; ARI, Alpay; GEDİZLİOĞLU, Muhteşem

2016-01-01

Introduction To investigate the existence of peripheral and optic neuropathies in asymptomatic individuals with hepatitis C infection. Methods Thirty consecutive patients who were followed in a hepatitis C outpatient clinic were recruited for electrophysiological evaluation together with 30 age- and gender-compatible healthy controls. All patients had a detailed neurological examination. The information regarding the disease duration and management with interferons were collected. Nerve conduction studies and visual evoked potentials (VEP) were recorded in all subjects. The results of the patient and control groups were statistically compared. Results Of the patients with hepatitis C infection, 16 were females and 14 males. The mean age was 57.5 years, and the average disease duration was 6.43 years. The P100 latencies in the patient group were within normal limits, while the amplitudes were meaningfully small by comparison with the controls. There were some abnormalities in the nerve conduction studies of 15 patients. Sensorial neuropathy was detected in two patients, sensorimotor polyneuropathy in four, carpal tunnel syndrome in seven, and carpal tunnel syndrome and sensorimotor polyneuropathy as comorbid states in another two patients. The nerve conduction studies and VEP parameters were entirely normal in the control group. Conclusion Hepatitis C-related neurological abnormalities may occur both in the central and peripheral nervous system. Mononeuritis multiplex, sensorial axonal neuropathy, and multiple mononeuropathies are some of the presentations of the peripheral nervous system involvement. The mode of infection is considered to be via vasculitic mechanisms. In addition, optic neuropathy is a known complication of interferon treatment. Autoantibodies, cytokines, chemokines, and cryoglobulins are accused to play roles in the pathogenesis. In this study, we investigated the involvement of the peripheral nervous system and optic nerves in a group of patients with hepatitis C. The results were in favor of peripheral nerve injury of various types and optic neuropathy of the axonal type. PMID:28360761

Essentials of photometry for clinical electrophysiology of vision.

PubMed

McCulloch, Daphne L; Hamilton, Ruth

2010-08-01

Electrophysiological testing of the visual system requires familiarity with photometry. This technical note outlines the concepts of photometry with a focus on information relevant to clinical ERG and VEP testing. Topics include photometric quantities, consideration of pupil size, specification of brief extended flash stimuli, and the influence of the spectral composition of visual stimuli. Standard units and terms are explained in the context of the ISCEV standards and guidelines for clinical electrophysiology of vision.

Assessment of visual disability using visual evoked potentials.

PubMed

Jeon, Jihoon; Oh, Seiyul; Kyung, Sungeun

2012-08-06

The purpose of this study is to validate the use of visual evoked potential (VEP) to objectively quantify visual acuity in normal and amblyopic patients, and determine if it is possible to predict visual acuity in disability assessment to register visual pathway lesions. A retrospective chart review was conducted of patients diagnosed with normal vision, unilateral amblyopia, optic neuritis, and visual disability who visited the university medical center for registration from March 2007 to October 2009. The study included 20 normal subjects (20 right eyes: 10 females, 10 males, ages 9-42 years), 18 unilateral amblyopic patients (18 amblyopic eyes, ages 19-36 years), 19 optic neuritis patients (19 eyes: ages 9-71 years), and 10 patients with visual disability having visual pathway lesions. Amplitude and latencies were analyzed and correlations with visual acuity (logMAR) were derived from 20 normal and 18 amblyopic subjects. Correlation of VEP amplitude and visual acuity (logMAR) of 19 optic neuritis patients confirmed relationships between visual acuity and amplitude. We calculated the objective visual acuity (logMAR) of 16 eyes from 10 patients to diagnose the presence or absence of visual disability using relations derived from 20 normal and 18 amblyopic eyes. Linear regression analyses between amplitude of pattern visual evoked potentials and visual acuity (logMAR) of 38 eyes from normal (right eyes) and amblyopic (amblyopic eyes) subjects were significant [y = -0.072x + 1.22, x: VEP amplitude, y: visual acuity (logMAR)]. There were no significant differences between visual acuity prediction values, which substituted amplitude values of 19 eyes with optic neuritis into function. We calculated the objective visual acuity of 16 eyes of 10 patients to diagnose the presence or absence of visual disability using relations of y = -0.072x + 1.22 (-0.072). This resulted in a prediction reference of visual acuity associated with malingering vs. real disability in a range >5.77 μV. The results could be useful, especially in cases of no obvious pale disc with trauma. Visual acuity quantification using absolute value of amplitude in pattern visual evoked potentials was useful in confirming subjective visual acuity for cutoff values >5.77 μV in disability evaluation to discriminate the malingering from real disability.

Submillisecond unmasked subliminal visual stimuli evoke electrical brain responses.

PubMed

Sperdin, Holger F; Spierer, Lucas; Becker, Robert; Michel, Christoph M; Landis, Theodor

2015-04-01

Subliminal perception is strongly associated to the processing of meaningful or emotional information and has mostly been studied using visual masking. In this study, we used high density 256-channel EEG coupled with an liquid crystal display (LCD) tachistoscope to characterize the spatio-temporal dynamics of the brain response to visual checkerboard stimuli (Experiment 1) or blank stimuli (Experiment 2) presented without a mask for 1 ms (visible), 500 µs (partially visible), and 250 µs (subliminal) by applying time-wise, assumption-free nonparametric randomization statistics on the strength and on the topography of high-density scalp-recorded electric field. Stimulus visibility was assessed in a third separate behavioral experiment. Results revealed that unmasked checkerboards presented subliminally for 250 µs evoked weak but detectable visual evoked potential (VEP) responses. When the checkerboards were replaced by blank stimuli, there was no evidence for the presence of an evoked response anymore. Furthermore, the checkerboard VEPs were modulated topographically between 243 and 296 ms post-stimulus onset as a function of stimulus duration, indicative of the engagement of distinct configuration of active brain networks. A distributed electrical source analysis localized this modulation within the right superior parietal lobule near the precuneus. These results show the presence of a brain response to submillisecond unmasked subliminal visual stimuli independently of their emotional saliency or meaningfulness and opens an avenue for new investigations of subliminal stimulation without using visual masking. © 2014 Wiley Periodicals, Inc.

Gender effect on neuromyelitis optica spectrum disorder with aquaporin4-immunoglobulin G.

PubMed

Kim, Sung-Min; Waters, Patrick; Woodhall, Mark; Kim, Yoo-Jin; Kim, Jin-Ah; Cheon, So Young; Lee, Sehoon; Jo, Seong Rae; Kim, Dong Gun; Jung, Kyeong Cheon; Lee, Kwang-Woo; Sung, Jung-Joon; Park, Kyung Seok

2017-07-01

Neuromyelitis optica spectrum disorder with aquaporin4-immunoglobulin G (NMOSD-AQP4) is an inflammatory disease characterised by a high female predominance. However, the effect of gender in patients with NMOSD-AQP4 has not been fully evaluated. The aim of this study was to determine the effect of gender in clinical manifestations and prognosis of patients with NMOSD-AQP4. The demographics, clinical and radiological characteristics, pattern reversal visual evoked potential (VEP) test results, and prognosis of 102 patients (18 males) with NMOSD-AQP4 were assessed. Male patients had a higher age at onset (48.7 vs 41 years, p = 0.037) and less optic neuritis as the onset attack (17% vs 44%, p = 0.026), higher tendency to manifest as isolated myelitis over the follow-up period (67% vs 28%, p = 0.005), fewer optic neuritis attacks per year (0.08 vs 0.27, p < 0.001), and shorter relative P100 latency on VEP testing (97.1% vs 108.3%, p = 0.001). Moreover, male gender was significantly associated with the absence of optic neuritis attacks over the follow-up period independent of their age of onset. In NMOSD-AQP4 patients, gender impacts on disease onset age and site of attack. This may be an important clue in identifying NMOSD-AQP4 patients with limited manifestations as well as in predicting their clinical courses.

Assessment of the effectiveness of head only and back-of-the-head electrical stunning of chickens

PubMed Central

Gibson, T. J.; Taylor, A. H.; Gregory, N. G.

2016-01-01

Abstract The study assesses the effectiveness of reversible head-only and back-of-the-head electrical stunning of chickens using 130–950 mA per bird at 50 Hz AC.Three trials were conducted to compare both stunning systems: (a) behavioural assessment of return of consciousness, (b) insensibility to thermal pain, and (c) assessment of return of brain activity with visually evoked potentials (VEPs).Assessment of behaviour suggested that the period of unconsciousness following head-only electrical stunning was shorter in hens compared to broilers.Stunning across the back-of-the-head delayed the time to return of brainstem function compared to stunning with standard head-only electrodes. Additionally, back-of-the-head stunning produced a more prolonged period of electroanalgesia compared to head-only.Based on examination of return of brain function with VEPs in hens, back-of-the-head stunning produced a shorter-lasting stun than standard head-only. However, even for standard head-only, the stun was notably shorter than previously reported. In some birds, brain function had returned within 9 s after the end of stunning.The results suggest that some birds may recover consciousness prior to or during the neck cut. Based on these findings, back-of-the-head stunning and standard head-only stunning of hens should not be recommended without further development. PMID:27023411

Steady-state visual evoked potentials as a research tool in social affective neuroscience

PubMed Central

Wieser, Matthias J.; Miskovic, Vladimir; Keil, Andreas

2017-01-01

Like many other primates, humans place a high premium on social information transmission and processing. One important aspect of this information concerns the emotional state of other individuals, conveyed by distinct visual cues such as facial expressions, overt actions, or by cues extracted from the situational context. A rich body of theoretical and empirical work has demonstrated that these socio-emotional cues are processed by the human visual system in a prioritized fashion, in the service of optimizing social behavior. Furthermore, socio-emotional perception is highly dependent on situational contexts and previous experience. Here, we review current issues in this area of research and discuss the utility of the steady-state visual evoked potential (ssVEP) technique for addressing key empirical questions. Methodological advantages and caveats are discussed with particular regard to quantifying time-varying competition among multiple perceptual objects, trial-by-trial analysis of visual cortical activation, functional connectivity, and the control of low-level stimulus features. Studies on facial expression and emotional scene processing are summarized, with an emphasis on viewing faces and other social cues in emotional contexts, or when competing with each other. Further, because the ssVEP technique can be readily accommodated to studying the viewing of complex scenes with multiple elements, it enables researchers to advance theoretical models of socio-emotional perception, based on complex, quasi-naturalistic viewing situations. PMID:27699794

A Genome-Wide Analysis of Populations from European Russia Reveals a New Pole of Genetic Diversity in Northern Europe

PubMed Central

Khrunin, Andrey V.; Khokhrin, Denis V.; Filippova, Irina N.; Esko, Tõnu; Nelis, Mari; Bebyakova, Natalia A.; Bolotova, Natalia L.; Klovins, Janis; Nikitina-Zake, Liene; Rehnström, Karola; Ripatti, Samuli; Schreiber, Stefan; Franke, Andre; Macek, Milan; Krulišová, Veronika; Lubinski, Jan; Metspalu, Andres; Limborska, Svetlana A.

2013-01-01

Several studies examined the fine-scale structure of human genetic variation in Europe. However, the European sets analyzed represent mainly northern, western, central, and southern Europe. Here, we report an analysis of approximately 166,000 single nucleotide polymorphisms in populations from eastern (northeastern) Europe: four Russian populations from European Russia, and three populations from the northernmost Finno-Ugric ethnicities (Veps and two contrast groups of Komi people). These were compared with several reference European samples, including Finns, Estonians, Latvians, Poles, Czechs, Germans, and Italians. The results obtained demonstrated genetic heterogeneity of populations living in the region studied. Russians from the central part of European Russia (Tver, Murom, and Kursk) exhibited similarities with populations from central–eastern Europe, and were distant from Russian sample from the northern Russia (Mezen district, Archangelsk region). Komi samples, especially Izhemski Komi, were significantly different from all other populations studied. These can be considered as a second pole of genetic diversity in northern Europe (in addition to the pole, occupied by Finns), as they had a distinct ancestry component. Russians from Mezen and the Finnic-speaking Veps were positioned between the two poles, but differed from each other in the proportions of Komi and Finnic ancestries. In general, our data provides a more complete genetic map of Europe accounting for the diversity in its most eastern (northeastern) populations. PMID:23505534

Risk factors for progressive axonal degeneration of the retinal nerve fibre layer in multiple sclerosis patients.

PubMed

Garcia-Martin, Elena; Pueyo, Victoria; Almarcegui, Carmen; Martin, Jesus; Ara, Jose R; Sancho, Eva; Pablo, Luis E; Dolz, Isabel; Fernandez, Javier

2011-11-01

To quantify structural and functional degeneration in the retinal nerve fibre layer (RNFL) of patients with multiple sclerosis (MS) over a 2-year time period, and to analyse the effect of prior optic neuritis (ON) as well as the duration and incidence of MS relapses. 166 MS patients and 120 healthy controls underwent assessment of visual acuity and colour vision, visual field examination, optical coherence tomography, scanning laser polarimetry and visual evoked potentials (VEPs). All subjects were re-evaluated after a period of 12 and 24 months. Changes in the optic nerve were detected by structural measurements but not by functional assessments. Changes registered in MS patients were greater than changes in healthy controls (p<0.05). Eyes with previous ON showed a greater reduction of parameters in the baseline evaluation, but RNFL atrophy was not significantly greater in the longitudinal study. Patients with MS relapses showed a greater reduction of RNFL thickness and VEP amplitude compared with non-relapsing cases. Patients with and without treatment showed similar measurement reduction, but the non-treated group had a significantly higher increase in Expanded Disability Status Scale (p=0.029). MS causes progressive axonal loss in the optic nerve, regardless of a history of ON. This ganglion cell atrophy occurs in all eyes but is more marked in MS eyes than in healthy eyes.

Querectin improves myelin repair of optic chiasm in lyolecithin-induced focal demyelination model.

PubMed

Naeimi, Reza; Baradaran, Saeideh; Ashrafpour, Manouchehr; Moghadamnia, Ali Akbar; Ghasemi-Kasman, Maryam

2018-05-01

Although the beneficial effects of quercetin on oligodendrocyte precursor cell (OPCs) population has been evaluated in-vitro, there are few studies about the effects of quercetin on myelin repair in the context of demyelination. The aim of this study was to investigate the effects of querectin on functional recovery and myelin repair of optic chiasm in lysolecithin (LPC)-induced demyelination model. Demyelination was induced by local injection of LPC 1% (2 μl) into rat optic chiasm. Querectin at doses 25 or 50 mg/kg was administrated daily by oral gavage for 7 or 14 days post LPC. Visual evoked potential (VEPs) recordings were used to assess the functional property of the optic pathway. Immunostaining and myelin staining were performed on brain sections 7 or 14 days post lesion. Electrophysiological data indicated that LPC injection increased the latency of VEPs waves and quercetin effectively reduced the delay of visual signals. The level of glial activation was alleviated in animals under treatment of quercetin compared to vehicle group. Furthermore, quercetin treatment decreased the extent of demyelination areas and increased the remyelination process following LPC injection. Overall, our findings indicate that quercetin could remarkably improve the functional recovery of the optic pathway by its protective effects on myelin sheath and attenuation of glial activation. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

Comparison of the efficacies of patching and penalization therapies for the treatment of amblyopia patients

PubMed Central

Cabi, Cemalettin; Sayman Muslubas, Isil Bahar; Aydin Oral, Ayse Yesim; Dastan, Metin

2014-01-01

AIM To compare the efficacies of patching and penalization therapies for the treatment of amblyopia patients. METHODS The records of 64 eyes of 50 patients 7 to 16y of age who had presented to our clinics with a diagnosis of amblyopia, were evaluated retrospectively. Forty eyes of 26 patients who had received patching therapy and 24 eyes of 24 patients who had received penalization therapy included in this study. The latencies and amplitudes of visual evoked potential (VEP) records and best corrected visual acuities (BCVA) of these two groups were compared before and six months after the treatment. RESULTS In both patching and the penalization groups, the visual acuities increased significantly following the treatments (P<0.05). The latency measurements of the P100 wave obtained at 1.0°, 15 arc min. Patterns of both groups significantly decreased following the 6-months-treatment. However, the amplitude measurements increased (P<0.05). CONCLUSION The patching and the penalization methods, which are the main methods used in the treatment of amblyopia, were also effective over the age of 7y, which has been accepted as the critical age for the treatment of amblyopia. PMID:24967195

Effects of the AMPA Antagonist ZK 200775 on Visual Function: A Randomized Controlled Trial

PubMed Central

Bergholz, Richard; Staks, Thomas; Rüther, Klaus

2010-01-01

Background ZK 200775 is an antagonist at the α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor and had earned attention as a possible neuroprotective agent in cerebral ischemia. Probands receiving the agent within phase I trials reported on an alteration of visual perception. In this trial, the effects of ZK 200775 on the visual system were analyzed in detail. Methodology In a randomised controlled trial we examined eyes and vision before and after the intravenous administration of two different doses of ZK 200775 and placebo. There were 3 groups of 6 probands each: Group 1 recieved 0.03 mg/kg/h, group 2 0.75 mg/kg/h of ZK 200775, the control group received 0.9% sodium chloride solution. Probands were healthy males aged between 57 and 69 years. The following methods were applied: clinical examination, visual acuity, ophthalmoscopy, colour vision, rod absolute threshold, central visual field, pattern-reversal visual evoked potentials (pVEP), ON-OFF and full-field electroretinogram (ERG). Principal Findings No effect of ZK 200775 was seen on eye position or motility, stereopsis, pupillary function or central visual field testing. Visual acuity and dark vision deteriorated significantly in both treated groups. Color vision was most remarkably impaired. The dark-adapted ERG revealed a reduction of oscillatory potentials (OP) and partly of the a- and b-wave, furthermore an alteration of b-wave morphology and an insignificantly elevated b/a-ratio. Cone-ERG modalities showed decreased amplitudes and delayed implicit times. In the ON-OFF ERG the ON-answer amplitudes increased whereas the peak times of the OFF-answer were reduced. The pattern VEP exhibited lower amplitudes and prolonged peak times. Conclusions The AMPA receptor blockade led to a strong impairment of typical OFF-pathway functions like color vision and the cone ERG. On the other hand the ON-pathway as measured by dark vision and the scotopic ERG was affected as well. This further elucidates the interdependence of both pathways. Trial Registration ClinicalTrials.gov NCT00999284 PMID:20711429

Color vision in attention-deficit/hyperactivity disorder: a pilot visual evoked potential study.

PubMed

Kim, Soyeon; Banaschewski, Tobias; Tannock, Rosemary

2015-01-01

Individuals with attention-deficit/hyperactivity disorder (ADHD) are reported to manifest visual problems (including ophthalmological and color perception, particularly for blue-yellow stimuli), but findings are inconsistent. Accordingly, this study investigated visual function and color perception in adolescents with ADHD using color Visual Evoked Potentials (cVEP), which provides an objective measure of color perception. Thirty-one adolescents (aged 13-18), 16 with a confirmed diagnosis of ADHD, and 15 healthy peers, matched for age, gender, and IQ participated in the study. All underwent an ophthalmological exam, as well as electrophysiological testing color Visual Evoked Potentials (cVEP), which measured the latency and amplitude of the neural P1 response to chromatic (blue-yellow, red-green) and achromatic stimuli. No intergroup differences were found in the ophthalmological exam. However, significantly larger P1 amplitude was found for blue and yellow stimuli, but not red/green or achromatic stimuli, in the ADHD group (particularly in the medicated group) compared to controls. Larger amplitude in the P1 component for blue-yellow in the ADHD group compared to controls may account for the lack of difference in color perception tasks. We speculate that the larger amplitude for blue-yellow stimuli in early sensory processing (P1) might reflect a compensatory strategy for underlying problems including compromised retinal input of s-cones due to hypo-dopaminergic tone. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

Defective motion processing in children with cerebral visual impairment due to periventricular white matter damage.

PubMed

Weinstein, Joel M; Gilmore, Rick O; Shaikh, Sumera M; Kunselman, Allen R; Trescher, William V; Tashima, Lauren M; Boltz, Marianne E; McAuliffe, Matthew B; Cheung, Albert; Fesi, Jeremy D

2012-07-01

We sought to characterize visual motion processing in children with cerebral visual impairment (CVI) due to periventricular white matter damage caused by either hydrocephalus (eight individuals) or periventricular leukomalacia (PVL) associated with prematurity (11 individuals). Using steady-state visually evoked potentials (ssVEP), we measured cortical activity related to motion processing for two distinct types of visual stimuli: 'local' motion patterns thought to activate mainly primary visual cortex (V1), and 'global' or coherent patterns thought to activate higher cortical visual association areas (V3, V5, etc.). We studied three groups of children: (1) 19 children with CVI (mean age 9y 6mo [SD 3y 8mo]; 9 male; 10 female); (2) 40 neurologically and visually normal comparison children (mean age 9y 6mo [SD 3y 1mo]; 18 male; 22 female); and (3) because strabismus and amblyopia are common in children with CVI, a group of 41 children without neurological problems who had visual deficits due to amblyopia and/or strabismus (mean age 7y 8mo [SD 2y 8mo]; 28 male; 13 female). We found that the processing of global as opposed to local motion was preferentially impaired in individuals with CVI, especially for slower target velocities (p=0.028). Motion processing is impaired in children with CVI. ssVEP may provide useful and objective information about the development of higher visual function in children at risk for CVI. © The Authors. Journal compilation © Mac Keith Press 2011.

Retinotopic Distribution of Structural and Functional Damages following Bright Light Exposure of Juvenile Rats

PubMed Central

Polosa, Anna; Liu, Wenwen; Lachapelle, Pierre

2016-01-01

In the present study, we aimed at better understanding the short (acute) and long term (chronic) degenerative processes characterizing the juvenile rat model of light-induced retinopathy. Electroretinograms, visual evoked potentials (VEP), retinal histology and western blots were obtained from juvenile albino Sprague-Dawley rats at preselected postnatal ages (from P30 to P400) following exposure to 10,000 lux from P14 to P28. Our results show that while immediately following the cessation of exposure, photoreceptor degeneration was concentrated within a well delineated area of the superior retina (i.e. the photoreceptor hole), with time, this hole continued to expand to form an almost photoreceptor-free region covering most of superior-inferior axis. By the end of the first year of life, only few photoreceptors remained in the far periphery of the superior hemiretina. Interestingly, despite a significant impairment of the outer retinal function, the retinal output (VEP) was maintained in the early phase of this retinopathy. Our findings thus suggest that postnatal exposure to a bright luminous environment triggers a degenerative process that continues to impair the retinal structure and function (mostly at the photoreceptor level) long after the cessation of the exposure regimen (more than 1 year documented herein). Given the slow degenerative process triggered following postnatal bright light exposure, we believe that our model represents an attractive alternative (to other more genetic models) to study the pathophysiology of photoreceptor-induced retinal degeneration as well as therapeutic strategies to counteract it. PMID:26784954

Online Reduction of Artifacts in EEG of Simultaneous EEG-fMRI Using Reference Layer Adaptive Filtering (RLAF).

PubMed

Steyrl, David; Krausz, Gunther; Koschutnig, Karl; Edlinger, Günter; Müller-Putz, Gernot R

2018-01-01

Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) allow us to study the active human brain from two perspectives concurrently. Signal processing based artifact reduction techniques are mandatory for this, however, to obtain reasonable EEG quality in simultaneous EEG-fMRI. Current artifact reduction techniques like average artifact subtraction (AAS), typically become less effective when artifact reduction has to be performed on-the-fly. We thus present and evaluate a new technique to improve EEG quality online. This technique adds up with online AAS and combines a prototype EEG-cap for reference recordings of artifacts, with online adaptive filtering and is named reference layer adaptive filtering (RLAF). We found online AAS + RLAF to be highly effective in improving EEG quality. Online AAS + RLAF outperformed online AAS and did so in particular online in terms of the chosen performance metrics, these being specifically alpha rhythm amplitude ratio between closed and opened eyes (3-45% improvement), signal-to-noise-ratio of visual evoked potentials (VEP) (25-63% improvement), and VEPs variability (16-44% improvement). Further, we found that EEG quality after online AAS + RLAF is occasionally even comparable with the offline variant of AAS at a 3T MRI scanner. In conclusion RLAF is a very effective add-on tool to enable high quality EEG in simultaneous EEG-fMRI experiments, even when online artifact reduction is necessary.

Effects of albendazole combined with TSII-A (a Chinese herb compound) on optic neuritis caused by Angiostrongylus cantonensis in BALB/c mice.

PubMed

Feng, Feng; Feng, Ying; Liu, Zhen; Li, Wei-Hua; Wang, Wen-Cong; Wu, Zhong-Dao; Lv, Zhiyue

2015-11-25

Angiostrongylus cantonensis (A. cantonensis) infection can lead to optic neuritis, retinal inflammation, damage to ganglion cells, demyelination of optic nerve and visual impairment. Combined therapy of albendazole and dexamethasone is a common treatment for the disease in the clinic, but it plays no role in vision recovery. Therefore, it has been necessary to explore alternative therapies to treat this disease. Previous studies reported the neuro-productive effects of two constituents of Danshen (a Chinese herb)-tanshinone II-A (TSII-A) and cryptotanshinone (CPT), and this study aims to evaluate the impacts of TSII-A or CPT combined with albendazole on optic neuritis caused by A. cantonensis infection in a murine model. To assess the effects of TSII-A or CPT combined with albendazole on optic neuritis due to the infection, mice were divided into six groups, including the normal control group, infection group and four treatment groups (albendazole group, albendazole combined with dexamethasone group, albendazole combined with CPT group and albendazole combined with TSII-A group). The infection group and treatment groups were infected with A. cantonensis and the treatment groups received interventions from 14 dpi (days post infection), respectively. At 21 dpi, the visual acuity of mice in each group was examined by visual evoked potential (VEP). The pathologic alteration of the retina and optic nerve were observed by hematoxylin and eosin (H&E) staining and transmission electronic microscopy (TEM). Infection of A. cantonensis caused prolonged VEP latency, obvious inflammatory cell infiltration in the retina, damaged retinal ganglions and retinal swelling, followed by optic nerve fibre demyelination and a decreasing number of axons at 21 dpi. In treatment groups, albendazole could not alleviate the above symptoms; albendazole combined with dexamethasone lessened the inflammation of the retina, but was futile for the other changes; however, albendazole combined with CPT and albendazole combined with TSII-A showed obvious effects on the recovery of prolonged VEP latency, destruction and reduction of ganglion cells, optic nerve demyelination and axon loss. Compared with albendazole-CPT compound, albendazole combined with TSII-A was more effective. The current study demonstrates that albendazole combined with TSII-A plays a more effective role in treating optic neuritis caused by A. cantonensis in mice than with dexamethasone, as applied in conventional treatment, indicating that albendazole combined with TSII-A might be an alternate therapy for this parasitic disease in the clinic.

Visual Sensitivities and Discriminations and Their Role in Aviation

DTIC Science & Technology

1987-10-30

both x and y, Aimn can be found by using one quarter of the plane. Hence 2P0r far.eco(-keosy) Ahm = i coa nv (coa x + kcoa y)cos mx dx dy since f(z,y...198-201. 142. Neima D, LeBlanc R & Regan D (1984) Visual field defects in ocular hypertension and glaucoma . Arch Ophthalmol 102, 1042-5. 143. Regan D...Neima D (1984) Visual fatigue and VEPs in multiple sclerosis, glaucoma , ocular hypertension and Parkinson’s disease. J Neurol Neurosurg Psychiat 47

Divergence of dim-light vision among bats (order: Chiroptera) as estimated by molecular and electrophysiological methods.

PubMed

Liu, He-Qun; Wei, Jing-Kuan; Li, Bo; Wang, Ming-Shan; Wu, Rui-Qi; Rizak, Joshua D; Zhong, Li; Wang, Lu; Xu, Fu-Qiang; Shen, Yong-Yi; Hu, Xin-Tian; Zhang, Ya-Ping

2015-06-23

Dim-light vision is present in all bats, but is divergent among species. Old-World fruit bats (Pteropodidae) have fully developed eyes; the eyes of insectivorous bats are generally degraded, and these bats rely on well-developed echolocation. An exception is the Emballonuridae, which are capable of laryngeal echolocation but prefer to use vision for navigation and have normal eyes. In this study, integrated methods, comprising manganese-enhanced magnetic resonance imaging (MEMRI), f-VEP and RNA-seq, were utilized to verify the divergence. The results of MEMRI showed that Pteropodidae bats have a much larger superior colliculus (SC)/ inferior colliculus (IC) volume ratio (3:1) than insectivorous bats (1:7). Furthermore, the absolute visual thresholds (log cd/m(2)•s) of Pteropodidae (-6.30 and -6.37) and Emballonuridae (-3.71) bats were lower than those of other insectivorous bats (-1.90). Finally, genes related to the visual pathway showed signs of positive selection, convergent evolution, upregulation and similar gene expression patterns in Pteropodidae and Emballonuridae bats. Different results imply that Pteropodidae and Emballonuridae bats have more developed vision than the insectivorous bats and suggest that further research on bat behavior is warranted.

Visual evoked potential measurement of contrast sensitivity in a case of retinal laser injury reveals visual function loss despite normal acuity

NASA Astrophysics Data System (ADS)

Glickman, Randolph D.; Harrison, Joseph M.; Zwick, Harry; Longbotham, Harold G.; Ballentine, Charles S.; Pierce, Bennie

1996-04-01

Although visual function following retinal laser injuries has traditionally been assessed by measuring visual acuity, this measure only indicates the highest spatial frequency resolvable under high-contrast viewing conditions. Another visual psychophysical parameter is contrast sensitivity (CS), which measures the minimum contrast required for detection of targets over a range of spatial frequencies, and may evaluate visual mechanisms that do not directly subserve acuity. We used the visual evoked potential (VEP) to measure CS in a population of normal subjects and in patients with ophthalmic conditions affecting retinal function, including one patient with a laser injury in the macula. In this patient, the acuity had recovered from

Neurophysiological assessment of auditory, peripheral nerve, somatosensory, and visual system functions after developmental exposure to ethanol vapors.

PubMed

Boyes, William K; Degn, Laura L; Martin, Sheppard A; Lyke, Danielle F; Hamm, Charles W; Herr, David W

2014-01-01

Ethanol-blended gasoline entered the market in response to demand for domestic renewable energy sources, and may result in increased inhalation of ethanol vapors in combination with other volatile gasoline constituents. It is important to understand potential risks of inhalation of ethanol vapors by themselves, and also as a baseline for evaluating the risks of ethanol combined with a complex mixture of hydrocarbon vapors. Because sensory dysfunction has been reported after developmental exposure to ethanol, we evaluated the effects of developmental exposure to ethanol vapors on neurophysiological measures of sensory function as a component of a larger project evaluating developmental ethanol toxicity. Pregnant Long-Evans rats were exposed to target concentrations 0, 5000, 10,000, or 21,000 ppm ethanol vapors for 6.5h/day over GD9-GD20. Sensory evaluations of male offspring began between PND106 and PND128. Peripheral nerve function (compound action potentials, nerve conduction velocity (NCV)), somatosensory (cortical and cerebellar evoked potentials), auditory (brainstem auditory evoked responses), and visual evoked responses were assessed. Visual function assessment included pattern elicited visual evoked potentials (VEPs), VEP contrast sensitivity, and electroretinograms recorded from dark-adapted (scotopic), light-adapted (photopic) flashes, and UV flicker and green flicker. No consistent concentration-related changes were observed for any of the physiological measures. The results show that gestational exposure to ethanol vapor did not result in detectable changes in peripheral nerve, somatosensory, auditory, or visual function when the offspring were assessed as adults. Published by Elsevier Inc.

Effort towards symmetric removal and surface smoothening of 1.3-GHz niobium single-cell cavity in vertical electropolishing using a unique cathode

NASA Astrophysics Data System (ADS)

Chouhan, Vijay; Kato, Shigeki; Nii, Keisuke; Yamaguchi, Takanori; Sawabe, Motoaki; Hayano, Hitoshi; Ida, Yoshiaki

2017-08-01

A detailed study on vertical electropolishing (VEP) of a 1.3-GHz single-cell niobium coupon cavity, which contains six coupons and four viewports at different positions, is reported. The cavity was vertically electropolished using a conventional rod and three types of unique cathodes named as Ninja cathodes, which were designed to have four retractable blades made of either an insulator or a metal or a combination of both. This study reveals the effect of the cathodes and their rotation speed on uniformity in removal thickness and surface morphology at different positions inside the cavity. Removal thickness was measured at several positions of the cavity using an ultrasonic thickness gauge and the surface features of the coupons were examined by an optical microscope and a surface profiler. The Ninja cathode with partial metallic blades was found to be effective not only in reducing asymmetric removal, which is one of the major problems in VEP and might be caused by the accumulation of hydrogen (H2 ) gas bubbles on the top iris of the cavity, but also in yielding a smooth surface of the entire cavity. A higher rotation speed of the Ninja cathode prevents bubble accumulation on the upper iris, and might result in a viscous layer of similar thickness in the cavity cell. Moreover, a higher electric field at the equator owing to the proximity of partial metallic blades to the equator surface resulted in a smooth surface. The effects of H2 gas bubbles and stirring were also observed in lab EP experiments.

Effect of chromatic filters on visual performance in individuals with mild traumatic brain injury (mTBI): A pilot study.

PubMed

Fimreite, Vanessa; Willeford, Kevin T; Ciuffreda, Kenneth J

2016-01-01

Spectral filters have been used clinically in patients with mild traumatic brain injury (mTBI). However, they have not been formally assessed using objective techniques in this population. Thus, the aim of the present pilot study was to determine the effect of spectral filters on reading performance and visuo-cortical responsivity in adults with mTBI. 12 adults with mTBI/concussion were tested. All reported photosensitivity and reading problems. They were compared to 12 visually-normal, asymptomatic adults. There were several test conditions: three luminance-matched control filters (gray neutral density, blue, and red), the patient-selected 'precision tint lens' that provided the most comfort and clarity of text using the Intuitive Colorimeter System, and baseline without any filters. The Visagraph was used to assess reading eye movements and reading speed objectively with each filter. In addition, both the amplitude and latency of the visual-evoked potential (VEP) were assessed with the same filters. There were few significant group differences in either the reading-related parameters or VEP latency for any of the test filter conditions. Subjective improvements were noted in most with mTBI (11/12). The majority of patients with mTBI chose a tinted filter that resulted in increased visual comfort. While significant findings based on the objective testing were found for some conditions, the subjective results suggest that precision tints should be considered as an adjunctive treatment in patients with mTBI and photosensitivity. Copyright © 2016 Spanish General Council of Optometry. Published by Elsevier España, S.L.U. All rights reserved.

Electrophysiology and optical coherence tomography to evaluate Parkinson disease severity.

PubMed

Garcia-Martin, Elena; Rodriguez-Mena, Diego; Satue, Maria; Almarcegui, Carmen; Dolz, Isabel; Alarcia, Raquel; Seral, Maria; Polo, Vicente; Larrosa, Jose M; Pablo, Luis E

2014-02-04

To evaluate correlations between visual evoked potentials (VEP), pattern electroretinogram (PERG), and macular and retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT) and the severity of Parkinson disease (PD). Forty-six PD patients and 33 age and sex-matched healthy controls were enrolled, and underwent VEP, PERG, and OCT measurements of macular and RNFL thicknesses, and evaluation of PD severity using the Hoehn and Yahr scale to measure PD symptom progression, the Schwab and England Activities of Daily Living Scale (SE-ADL) to evaluate patient quality of life (QOL), and disease duration. Logistical regression was performed to analyze which measures, if any, could predict PD symptom progression or effect on QOL. Visual functional parameters (best corrected visual acuity, mean deviation of visual field, PERG positive (P) component at 50 ms -P50- and negative (N) component at 95 ms -N95- component amplitude, and PERG P50 component latency) and structural parameters (OCT measurements of RNFL and retinal thickness) were decreased in PD patients compared with healthy controls. OCT measurements were significantly negatively correlated with the Hoehn and Yahr scale, and significantly positively correlated with the SE-ADL scale. Based on logistical regression analysis, fovea thickness provided by OCT equipment predicted PD severity, and QOL and amplitude of the PERG N95 component predicted a lower SE-ADL score. Patients with greater damage in the RNFL tend to have lower QOL and more severe PD symptoms. Foveal thicknesses and the PERG N95 component provide good biomarkers for predicting QOL and disease severity.

Evaluation of transcranial surgical decompression of the optic canal as a treatment option for traumatic optic neuropathy.

PubMed

He, Zhenhua; Li, Qiang; Yuan, Jingmin; Zhang, Xinding; Gao, Ruiping; Han, Yanming; Yang, Wenzhen; Shi, Xuefeng; Lan, Zhengbo

2015-07-01

Traumatic optic neuropathy (TON) is a serious complication of head trauma, with the incidence rate ranging from 0.5% to 5%. The two treatment options widely practiced for TON are: (i) high-dose corticosteroid therapy and (ii) surgical decompression. However, till date, there is no consensus on the treatment protocol. This study aimed to evaluate the therapeutic efficacy of transcranial decompression of optic canal in TON patients. A total of 39 patients with visual loss resulting from TON between January 2005 and June 2013 were retrospectively reviewed for preoperative vision, preoperative image, visual evoked potential (VEP), surgical approach, postoperative visual acuity, complications, and follow-up results. All these patients underwent transcranial decompression of optic canal. During the three-month follow-up period, among the 39 patients, 21 showed an improvement in their eyesight, 6 recovered to standard logarithmic visual acuity chart "visible," 10 could count fingers, 2 could see hand movement, and 3 regained light sensation. Visual evoked potential could be used as an important preoperative and prognostic evaluation parameter for TON patients. Once TON was diagnosed, surgery is a promising therapeutic option, especially when a VEP wave is detected, irrespective of the HRCT scan findings. Operative time between trauma and operation is not necessary reference to assess the therapeutic effect of surgical decompression. The poor results of this procedure may be related to the severity of optic nerve injury. The patient's age is an important factor affecting the surgical outcomes. Copyright © 2015 Elsevier B.V. All rights reserved.

Understanding disparities among diagnostic technologies in glaucoma.

PubMed

De Moraes, Carlos Gustavo V; Liebmann, Jeffrey M; Ritch, Robert; Hood, Donald C

2012-07-01

To investigate causes of disagreement among 3 glaucoma diagnostic techniques: standard automated achromatic perimetry (SAP), the multifocal visual evoked potential technique (mfVEP), and optical coherence tomography (OCT). In a prospective cross-sectional study, 138 eyes of 69 patients with glaucomatous optic neuropathy were tested using SAP, the mfVEP, and OCT. Eyes with the worse and better mean deviations (MDs) were analyzed separately. If the results of 2 tests were consistent for the presence of an abnormality in the same topographic site, that abnormality was considered a true glaucoma defect. If a third test missed that abnormality (false-negative result), the reasons for disparity were investigated. Eyes with worse MD (mean [SD], -6.8 [8.0] dB) had better agreements among tests than did eyes with better MD (-2.5 [3.5] dB, P<.01). For the 94 of 138 hemifields with abnormalities of the more advanced eyes, the 3 tests were consistent in showing the same hemifield abnormality in 50 hemifields (53%), and at least 2 tests were abnormal in 65 of the 94 hemifields (69%). The potential explanations for the false-negative results fell into 2 general categories: inherent limitations of each technique to detect distinct features of glaucoma and individual variability and the distribution of normative values used to define statistically significant abnormalities. All the cases of disparity could be explained by known limitations of each technique and interindividual variability, suggesting that the agreement among diagnostic tests may be better than summary statistics suggest and that disagreements between tests do not indicate discordance in the structure-function relationship.

Intravitreal erythropoietin injection in late-stage optic neuropathy: a safety study on human.

PubMed

Acar, Ugur; Kucuk, Bekir; Sevinc, Mehmet Koray; Aykas, Seckin; Erdurmus, Mesut; Sobaci, Gungor

2018-06-01

To evaluate the whether intravitreal erythropoietin (EPO) administration has any beneficial or adverse effect in patients with late-stage optic neuropathy (ON) or not. The study examined 16 eyes of 16 patients who had late-stage ON and ≥1/20 best-corrected visual acuity (BCVA) in their affected eye. There were nonarteritic ischemic ON in 10 (62.5%) eyes, traumatic ON in 4 (25.0%) eyes and methanol-induced ON in 2 (12.5%) eyes. Using pars plana approach, 2000 IU/0.2 ml EPO was administered intravitreally with a 30-gauge needle. Injections were administered three times with 6-week intervals. We compared the differences in the BCVA, intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, pattern visual evoked potentials (p-VEP) and pattern electroretinography (p-ERG) parameters performed at initial examination and final visits. The mean age of the patients was 52.38 ± 12.00 years; 2 (12.50%) of them were female, and 14 (87.50%) of them were male. The mean BCVA levels of 16 patients with optic atrophy were 1.12 ± 0.25 logMAR at the initial examination and 1.08 ± 0.26 logMAR at the final visit (p = 0.102). There was no statistically significant difference between the initial and final RNFL thicknesses, IOP values, p-ERG or p-VEP responses. Intravitreal EPO injections have no beneficial or detrimental effect on the late stage of ON. Further studies are necessary to compare our results in patients with ON in earlier stages.

Acute effects of theanine, caffeine and theanine-caffeine combination on attention.

PubMed

Kahathuduwa, Chanaka N; Dassanayake, Tharaka L; Amarakoon, A M Tissa; Weerasinghe, Vajira S

2017-07-01

l-theanine is a constituent of tea which is claimed to enhance cognitive functions. We aimed to determine whether theanine and theanine-caffeine combination have acute positive effects on cognitive and neurophysiological measures of attention, compared to caffeine (a positive control) and a placebo in healthy individuals. In a placebo-controlled, five-way crossover trial in 20 healthy male volunteers, we compared the effects of l-theanine (200 mg), caffeine (160 mg), their combination, black tea (one cup) and a placebo (distilled water) on cognitive (simple [SVRT] and recognition visual reaction time [RVRT]) and neurophysiological (event-related potentials [ERPs]) measures of attention. We also recorded visual (VEPs) and motor evoked potentials (MEPs) to examine any effects of treatments on peripheral visual and motor conduction, respectively. Mean RVRT was significantly improved by theanine (P = 0.019), caffeine (P = 0.043), and theanine-caffeine combination (P = 0.001), but not by tea (P = 0.429) or placebo (P = 0.822). VEP or MEP latencies or SVRT did not show significant inter-treatment differences. Theanine (P = 0.001) and caffeine (P = 0.001) elicited significantly larger mean peak-to-peak N2-P300 ERP amplitudes than the placebo, whereas theanine-caffeine combination elicited a significantly larger mean N2-P300 amplitude than placebo (P < 0.001), theanine (P = 0.029) or caffeine (P = 0.005). No significant theanine × caffeine interaction was observed for RVRT or N2-P300 amplitude. A dose of theanine equivalent of eight cups of back tea improves cognitive and neurophysiological measures of selective attention, to a degree that is comparable with that of caffeine. Theanine and caffeine seem to have additive effects on attention in high doses.

[Clinical symptoms and signs in Kimmerle anomaly].

PubMed

Split, Wojciech; Sawrasewicz-Rybak, Małgorzata

2002-01-01

The aim of the study was to consider Kimmerle anomaly (ponticulus posterior of the atlas) as an anatomic variant, which can cause a set of clinical symptoms and signs. A hundred and eight patients, 58 females and 50 males at the age of 18-59 years (M. 36.9 years, SD = 9.6) with radiologically verified Kimmerle anomaly were examined. A control group comprised 40 healthy subjects at the similar age range. The diagnosis of headaches was based on the criteria proposed by the IHS. A character of headaches, their localization, frequency, duration, number of days with headaches per year, circumstances associated with their onset and concomitant symptoms were evaluated. All the patients were subjected to electrophysiological studies (ENG, EEG and VEP). The results were statistically analyzed using a SPSS/PC+ computer system. It was revealed that clinical symptoms and signs in Kimmerle anomaly occurred most frequently in the third and fourth decade of life (65% of cases). These were most often tension-type headaches (50% of cases with headaches), vascular headaches (26% of cases) and neuralgia (24% of cases). Intensity of headaches was high. Headaches were accompanied by other complaints like vertigo (59% of cases) and in one third of cases--nausea. About 10% of patients also suffered from vomiting, paresthesia, dizziness, short periods of loss of consciousness. Sporadically--tinitus, drop attack, and vegetative symptoms. In cases without pain the most frequent signs were short periods of loss of consciousness, dizziness, and also nausea and dizziness. The EEG examination revealed pathology in 40% of patients with Kimmerle anomaly. The ENG examination in more than 33% of anomaly cases showed injury in the central part of vestibular system. Improper answers were reported in about 75% of the patients during the VEP examination.

EEG, evoked potentials and pulsed Doppler in asphyxiated term infants.

PubMed

Julkunen, Mia K; Himanen, Sari-Leena; Eriksson, Kai; Janas, Martti; Luukkaala, Tiina; Tammela, Outi

2014-09-01

To evaluate electroencephalograms (EEG), evoked potentials (EPs) and Doppler findings in the cerebral arteries as predictors of a 1-year outcome in asphyxiated newborn infants. EEG and EPs (brain stem auditory (BAEP), somatosensory (SEP), visual (VEP) evoked potentials) were assessed in 30 asphyxiated and 30 healthy term infants during the first days (range 1-8). Cerebral blood flow velocities (CBFV) were measured from the cerebral arteries using pulsed Doppler at ∼24h of age. EEG, EPs, Doppler findings, symptoms of hypoxic ischemic encephalopathy (HIE) and their combination were evaluated in predicting a 1-year outcome. An abnormal EEG background predicted poor outcome in the asphyxia group with a sensitivity of 67% and 81% specificity, and an abnormal SEP with 75% and 79%, respectively. Combining increased systolic CBFV (mean+3SD) with abnormal EEG or SEP improved the specificity, but not the sensitivity. The predictive values of abnormal BAEP and VEP were poor. Normal EEG and SEP predicted good outcome in the asphyxia group with sensitivities from 79% to 81%. The combination of normal EEG, normal SEP and systolic CBFV<3SD predicted good outcome with a sensitivity of 74% and 100% specificity. Combining abnormal EEG or EPs findings with increased systolic CBFV did not improve prediction of a poor 1-year outcome of asphyxiated infants. Normal EEG and normal SEP combined with systolic CBFV<3SD at about 24 h can be valuable in the prediction of normal 1-year outcome. Combining systolic CBFV at 24 h with EEG and SEP examinations can be of use in the prediction of normal 1-year outcome among asphyxiated infants. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

A New Visual Stimulation Program for Improving Visual Acuity in Children with Visual Impairment: A Pilot Study.

PubMed

Tsai, Li-Ting; Hsu, Jung-Lung; Wu, Chien-Te; Chen, Chia-Ching; Su, Yu-Chin

2016-01-01

The purpose of this study was to investigate the effectiveness of visual rehabilitation of a computer-based visual stimulation (VS) program combining checkerboard pattern reversal (passive stimulation) with oddball stimuli (attentional modulation) for improving the visual acuity (VA) of visually impaired (VI) children and children with amblyopia and additional developmental problems. Six children (three females, three males; mean age = 3.9 ± 2.3 years) with impaired VA caused by deficits along the anterior and/or posterior visual pathways were recruited. Participants received eight rounds of VS training (two rounds per week) of at least eight sessions per round. Each session consisted of stimulation with 200 or 300 pattern reversals. Assessments of VA (assessed with the Lea symbol VA test or Teller VA cards), visual evoked potential (VEP), and functional vision (assessed with the Chinese-version Functional Vision Questionnaire, FVQ) were carried out before and after the VS program. Significant gains in VA were found after the VS training [VA = 1.05 logMAR ± 0.80 to 0.61 logMAR ± 0.53, Z = -2.20, asymptotic significance (2-tailed) = 0.028]. No significant changes were observed in the FVQ assessment [92.8 ± 12.6 to 100.8 ±SD = 15.4, Z = -1.46, asymptotic significance (2-tailed) = 0.144]. VEP measurement showed improvement in P100 latency and amplitude or integration of the waveform in two participants. Our results indicate that a computer-based VS program with passive checkerboard stimulation, oddball stimulus design, and interesting auditory feedback could be considered as a potential intervention option to improve the VA of a wide age range of VI children and children with impaired VA combined with other neurological disorders.

A New Visual Stimulation Program for Improving Visual Acuity in Children with Visual Impairment: A Pilot Study

PubMed Central

Tsai, Li-Ting; Hsu, Jung-Lung; Wu, Chien-Te; Chen, Chia-Ching; Su, Yu-Chin

2016-01-01

The purpose of this study was to investigate the effectiveness of visual rehabilitation of a computer-based visual stimulation (VS) program combining checkerboard pattern reversal (passive stimulation) with oddball stimuli (attentional modulation) for improving the visual acuity (VA) of visually impaired (VI) children and children with amblyopia and additional developmental problems. Six children (three females, three males; mean age = 3.9 ± 2.3 years) with impaired VA caused by deficits along the anterior and/or posterior visual pathways were recruited. Participants received eight rounds of VS training (two rounds per week) of at least eight sessions per round. Each session consisted of stimulation with 200 or 300 pattern reversals. Assessments of VA (assessed with the Lea symbol VA test or Teller VA cards), visual evoked potential (VEP), and functional vision (assessed with the Chinese-version Functional Vision Questionnaire, FVQ) were carried out before and after the VS program. Significant gains in VA were found after the VS training [VA = 1.05 logMAR ± 0.80 to 0.61 logMAR ± 0.53, Z = –2.20, asymptotic significance (2-tailed) = 0.028]. No significant changes were observed in the FVQ assessment [92.8 ± 12.6 to 100.8 ±SD = 15.4, Z = –1.46, asymptotic significance (2-tailed) = 0.144]. VEP measurement showed improvement in P100 latency and amplitude or integration of the waveform in two participants. Our results indicate that a computer-based VS program with passive checkerboard stimulation, oddball stimulus design, and interesting auditory feedback could be considered as a potential intervention option to improve the VA of a wide age range of VI children and children with impaired VA combined with other neurological disorders. PMID:27148014

Characteristics of pediatric multiple sclerosis: The Turkish pediatric multiple sclerosis database.

PubMed

Yılmaz, Ünsal; Anlar, Banu; Gücüyener, Kıvılcım

2017-11-01

To document the clinical and paraclinical features of pediatric multiple sclerosis (MS) in Turkey. Data of MS patients with onset before age 18 years (n = 193) were collected from 27 pediatric neurology centers throughout Turkey. Earlier-onset (<12 years) and later-onset (≥12 years) groups were compared. There were 123 (63.7%) girls and 70 (36.3%) boys aged 4-17 years, median 14 years at disease onset. Family history of MS was 6.5%. The first presentation was polysymptomatic in 55.4% of patients, with brainstem syndromes (50.3%), sensory disturbances (44%), motor symptoms (33.2%), and optic neuritis (26.4%) as common initial manifestations. Nineteen children had facial paralysis and 10 had epileptic seizures at first attack; 21 (11%) were initially diagnosed with acute disseminated encephalomyelitis (ADEM). Oligoclonal bands were identified in 68% of patients. Magnetic resonance imaging revealed periventricular (96%), cortical/juxtacortical (64.2%), brainstem (63%), cerebellum (51.4%), and spinal cord (67%) involvement. Visual evoked potentials (VEP) were abnormal in 52%; serum 25-hydroxyvitamin D levels were low in 68.5% of patients. The earlier-onset group had a higher rate of infection/vaccination preceding initial attack, initial diagnosis of ADEM, longer interval between first 2 attacks, and more disability accumulating in the first 3 years of the disease. Brainstem and cerebellum are common sites of clinical and radiological involvement in pediatric-onset MS. VEP abnormalities are frequent even in patients without history of optic neuropathy. Vitamin D status does not appear to affect the course in early disease. MS beginning before 12 years of age has certain characteristics in history and course. Copyright © 2017 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.

Functional and morphological assessment of ocular structures and follow-up of patients with early-stage Parkinson's disease.

PubMed

Hasanov, Samir; Demirkilinc Biler, Elif; Acarer, Ahmet; Akkın, Cezmi; Colakoglu, Zafer; Uretmen, Onder

2018-05-09

To evaluate and follow-up of functional and morphological changes of the optic nerve and ocular structures prospectively in patients with early-stage Parkinson's disease. Nineteen patients with a diagnosis of early-stage Parkinson's disease and 19 age-matched healthy controls were included in the study. All participants were examined minimum three times at the intervals of at least 6 month following initial examination. Pattern visually evoked potentials (VEP), contrast sensitivity assessments at photopic conditions, color vision tests with Ishihara cards and full-field visual field tests were performed in addition to measurement of retinal nerve fiber layer (RNFL) thickness of four quadrants (top, bottom, nasal, temporal), central and mean macular thickness and macular volumes. Best corrected visual acuity was observed significantly lower in study group within all three examinations. Contrast sensitivity values of the patient group were significantly lower in all spatial frequencies. P100 wave latency of VEP was significantly longer, and amplitude was lower in patient group; however, significant deterioration was not observed during the follow-up. Although average peripapillary RNFL thickness was not significant between groups, RNFL thickness in the upper quadrant was thinner in the patient group. While there was no difference in terms of mean macular thickness and total macular volume values between the groups initially, a significant decrease occurred in the patient group during the follow-up. During the initial and follow-up process, a significant deterioration in visual field was observed in the patient group. Structural and functional disorders shown as electro-physiologically and morphologically exist in different parts of visual pathways in early-stage Parkinson's disease.

Inhibition of neutral sphingomyelinase decreases elevated levels of inducible nitric oxide synthase and apoptotic cell death in ocular hypertensive rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aslan, Mutay, E-mail: mutayaslan@akdeniz.edu.tr; Basaranlar, Goksun; Unal, Mustafa

Endoplasmic reticulum (ER) stress and excessive nitric oxide production via induction of inducible nitric oxide synthase (NOS2) have been implicated in the pathogenesis of neuronal retinal cell death in ocular hypertension. Neutral sphingomyelinase (N-SMase)/ceramide pathway can regulate NOS2 expression, hence this study determined the role of selective neutral sphingomyelinase (N-SMase) inhibition on retinal NOS2 levels, ER stress, apoptosis and visual evoked potentials (VEPs) in a rat model of elevated intraocular pressure (EIOP). NOS2 expression and retinal protein nitration were significantly greater in EIOP and significantly decreased with N-SMase inhibition. A significant increase was observed in retinal ER stress markers pPERK,more » CHOP and GRP78 in EIOP, which were not significantly altered by N-SMase inhibition. Retinal TUNEL staining showed increased apoptosis in all EIOP groups; however N-SMase inhibition significantly decreased the percent of apoptotic cells in EIOP. Caspase-3, -8 and -9 activities were significantly increased in EIOP and returned to baseline levels following N-SMase inhibition. Latencies of all VEP components were significantly prolonged in EIOP and shortened following N-SMase inhibition. Data confirm the role of nitrative injury in EIOP and highlight the protective effect of N-SMase inhibition in EIOP via down-regulation of NOS2 levels and nitrative stress. - Highlights: • Inhibition of N-SMase decreases NOS2 levels in ocular hypertension. • Inhibition of N-SMase decreases protein nitration in ocular hypertension. • Inhibition of N-SMase decreases caspase activation in ocular hypertension. • Inhibition of N-SMase decreases apoptosis in ocular hypertension.« less

Blindfolding during wakefulness causes decrease in sleep slow wave activity.

PubMed

Korf, Eva Magdalena; Mölle, Matthias; Born, Jan; Ngo, Hong-Viet V

2017-04-01

Slow wave activity (SWA, 0.5-4 Hz) represents the predominant EEG oscillatory activity during slow wave sleep (SWS). Its amplitude is considered in part a reflection of synaptic potentiation in cortical networks due to encoding of information during prior waking, with higher amplitude indicating stronger potentiation. Previous studies showed that increasing and diminishing specific motor behaviors produced corresponding changes in SWA in the respective motor cortical areas during subsequent SWS Here, we tested whether this relationship can be generalized to the visual system, that is, whether diminishing encoding of visual information likewise leads to a localized decrease in SWA over the visual cortex. Experiments were performed in healthy men whose eyes on two different days were or were not covered for 10.5 h before bedtime. The subject's EEG was recorded during sleep and, after sleep, visual evoked potentials (VEPs) were recorded. SWA during nonrapid eye movement sleep (NonREM sleep) was lower after blindfolding than after eyes open ( P  < 0.01). The decrease in SWA that was most consistent during the first 20 min of NonREM sleep, did not remain restricted to visual cortex regions, with changes over frontal and parietal cortical regions being even more pronounced. In the morning after sleep, the N75-P100 peak-to-peak-amplitude of the VEP was significantly diminished in the blindfolded condition. Our findings confirm a link between reduced wake encoding and diminished SWA during ensuing NonREM sleep, although this link appears not to be restricted to sensory cortical areas. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

Low-level laser therapy improves visual acuity in adolescent and adult patients with amblyopia.

PubMed

Ivandic, Boris T; Ivandic, Tomislav

2012-03-01

The purpose of this study was to examine the effects of low-level laser therapy (LLLT) on visual acuity in adolescent and adult patients with amblyopia. Currently, amblyopia can be treated successfully only in children. In this single-blinded, placebo-controlled study, 178 patients (mean age 46.8 years) with amblyopia caused by ametropia (110 eyes) or strabismus (121 eyes) were included. For LLLT, the area of the macula was irradiated through the conjunctiva from 1 cm distance for 30 sec with laser light (780 nm, 292 Hz, 1:1 duty cycle; average power 7.5 mW; spot area 3 mm(2)). The treatment was repeated on average 3.5 times, resulting in a mean total dose of 0.77 J/cm(2). No occlusion was applied, and no additional medication was administered. Best corrected distant visual acuity was determined using Snellen projection optotypes. In 12 patients (12 eyes), the multifocal visual evoked potential (M-VEP) was recorded. A control group of 20 patients (20 eyes) received mock treatment. Visual acuity improved in ∼90% of the eyes treated with LLLT (p<0.001), increasing by three or more lines in 56.2% and 53.6% of the eyes with amblyopia caused by ametropia and strabismus, respectively. The treatment effect was maintained for at least 6 months. The mean M-VEP amplitude increased by 1207 nV (p<0.001) and mean latency was reduced by 7 msec (p=0.14). No changes were noted in the control group. LLLT led to a significant improvement in visual acuity in adolescent and adult patients with amblyopia caused by ametropia or strabismus.

Divergence of dim-light vision among bats (order: Chiroptera) as estimated by molecular and electrophysiological methods

PubMed Central

Liu, He-Qun; Wei, Jing-Kuan; Li, Bo; Wang, Ming-Shan; Wu, Rui-Qi; Rizak, Joshua D.; Zhong, Li; Wang, Lu; Xu, Fu-Qiang; Shen, Yong-Yi; Hu, Xin-Tian; Zhang, Ya-Ping

2015-01-01

Dim-light vision is present in all bats, but is divergent among species. Old-World fruit bats (Pteropodidae) have fully developed eyes; the eyes of insectivorous bats are generally degraded, and these bats rely on well-developed echolocation. An exception is the Emballonuridae, which are capable of laryngeal echolocation but prefer to use vision for navigation and have normal eyes. In this study, integrated methods, comprising manganese-enhanced magnetic resonance imaging (MEMRI), f-VEP and RNA-seq, were utilized to verify the divergence. The results of MEMRI showed that Pteropodidae bats have a much larger superior colliculus (SC)/ inferior colliculus (IC) volume ratio (3:1) than insectivorous bats (1:7). Furthermore, the absolute visual thresholds (log cd/m2•s) of Pteropodidae (−6.30 and −6.37) and Emballonuridae (−3.71) bats were lower than those of other insectivorous bats (−1.90). Finally, genes related to the visual pathway showed signs of positive selection, convergent evolution, upregulation and similar gene expression patterns in Pteropodidae and Emballonuridae bats. Different results imply that Pteropodidae and Emballonuridae bats have more developed vision than the insectivorous bats and suggest that further research on bat behavior is warranted. PMID:26100095

Color coding of control room displays: the psychocartography of visual layering effects.

PubMed

Van Laar, Darren; Deshe, Ofer

2007-06-01

To evaluate which of three color coding methods (monochrome, maximally discriminable, and visual layering) used to code four types of control room display format (bars, tables, trend, mimic) was superior in two classes of task (search, compare). It has recently been shown that color coding of visual layers, as used in cartography, may be used to color code any type of information display, but this has yet to be fully evaluated. Twenty-four people took part in a 2 (task) x 3 (coding method) x 4 (format) wholly repeated measures design. The dependent variables assessed were target location reaction time, error rates, workload, and subjective feedback. Overall, the visual layers coding method produced significantly faster reaction times than did the maximally discriminable and the monochrome methods for both the search and compare tasks. No significant difference in errors was observed between conditions for either task type. Significantly less perceived workload was experienced with the visual layers coding method, which was also rated more highly than the other coding methods on a 14-item visual display quality questionnaire. The visual layers coding method is superior to other color coding methods for control room displays when the method supports the user's task. The visual layers color coding method has wide applicability to the design of all complex information displays utilizing color coding, from the most maplike (e.g., air traffic control) to the most abstract (e.g., abstracted ecological display).

A simple integrated system for electrophysiologic recordings in animals

PubMed Central

Slater, Bernard J.; Miller, Neil R.; Bernstein, Steven L.; Flower, Robert W.

2009-01-01

This technical note describes a modification to a fundus camera that permits simultaneous recording of pattern electroretinograms (pERGs) and pattern visual evoked potentials (pVEPs). The modification consists of placing an organic light-emitting diode (OLED) in the split-viewer pathway of a fundus camera, in a plane conjugate to the subject’s pupil. In this way, a focused image of the OLED can be delivered to a precisely known location on the retina. The advantage of using an OLED is that it can achieve high luminance while maintaining high contrast, and with minimal degradation over time. This system is particularly useful for animal studies, especially when precise retinal positioning is required. PMID:19137347

Wilderness experience in Rocky Mountain National Park 2002: Report to RMNP

USGS Publications Warehouse

Schuster, Elke; Johnson, S. Shea; Taylor, Jonathan G.

2004-01-01

The social science technique of Visitor Employed Photography [VEP] was used to obtain information from visitors about wilderness experiences. Visitors were selected at random from Park-designated wilderness trails, in proportion to their use, and asked to participate in the survey. Respondents were given single-use, 10-exposure cameras and photo-log diaries to record experiences. A total of 293 cameras were distributed, with a response rate of 87%. Following the development of the photos, a copy of the photos, two pertinent pages from the photo-log, and a follow-up survey were mailed to respondents. Fifty six percent of the follow-up surveys were returned. Findings from the two surveys were analyzed and compared.

The optimal code searching method with an improved criterion of coded exposure for remote sensing image restoration

NASA Astrophysics Data System (ADS)

He, Lirong; Cui, Guangmang; Feng, Huajun; Xu, Zhihai; Li, Qi; Chen, Yueting

2015-03-01

Coded exposure photography makes the motion de-blurring a well-posed problem. The integration pattern of light is modulated using the method of coded exposure by opening and closing the shutter within the exposure time, changing the traditional shutter frequency spectrum into a wider frequency band in order to preserve more image information in frequency domain. The searching method of optimal code is significant for coded exposure. In this paper, an improved criterion of the optimal code searching is proposed by analyzing relationship between code length and the number of ones in the code, considering the noise effect on code selection with the affine noise model. Then the optimal code is obtained utilizing the method of genetic searching algorithm based on the proposed selection criterion. Experimental results show that the time consuming of searching optimal code decreases with the presented method. The restoration image is obtained with better subjective experience and superior objective evaluation values.

A novel construction method of QC-LDPC codes based on CRT for optical communications

NASA Astrophysics Data System (ADS)

Yuan, Jian-guo; Liang, Meng-qi; Wang, Yong; Lin, Jin-zhao; Pang, Yu

2016-05-01

A novel construction method of quasi-cyclic low-density parity-check (QC-LDPC) codes is proposed based on Chinese remainder theory (CRT). The method can not only increase the code length without reducing the girth, but also greatly enhance the code rate, so it is easy to construct a high-rate code. The simulation results show that at the bit error rate ( BER) of 10-7, the net coding gain ( NCG) of the regular QC-LDPC(4 851, 4 546) code is respectively 2.06 dB, 1.36 dB, 0.53 dB and 0.31 dB more than those of the classic RS(255, 239) code in ITU-T G.975, the LDPC(32 640, 30 592) code in ITU-T G.975.1, the QC-LDPC(3 664, 3 436) code constructed by the improved combining construction method based on CRT and the irregular QC-LDPC(3 843, 3 603) code constructed by the construction method based on the Galois field ( GF( q)) multiplicative group. Furthermore, all these five codes have the same code rate of 0.937. Therefore, the regular QC-LDPC(4 851, 4 546) code constructed by the proposed construction method has excellent error-correction performance, and can be more suitable for optical transmission systems.

Feasibility and performance evaluation of generating and recording visual evoked potentials using ambulatory Bluetooth based system.

PubMed

Ellingson, Roger M; Oken, Barry

2010-01-01

Report contains the design overview and key performance measurements demonstrating the feasibility of generating and recording ambulatory visual stimulus evoked potentials using the previously reported custom Complementary and Alternative Medicine physiologic data collection and monitoring system, CAMAS. The methods used to generate visual stimuli on a PDA device and the design of an optical coupling device to convert the display to an electrical waveform which is recorded by the CAMAS base unit are presented. The optical sensor signal, synchronized to the visual stimulus emulates the brain's synchronized EEG signal input to CAMAS normally reviewed for the evoked potential response. Most importantly, the PDA also sends a marker message over the wireless Bluetooth connection to the CAMAS base unit synchronized to the visual stimulus which is the critical averaging reference component to obtain VEP results. Results show the variance in the latency of the wireless marker messaging link is consistent enough to support the generation and recording of visual evoked potentials. The averaged sensor waveforms at multiple CPU speeds are presented and demonstrate suitability of the Bluetooth interface for portable ambulatory visual evoked potential implementation on our CAMAS platform.

Light transmission and preference of eye patches for occlusion treatment.

PubMed

Heo, Hwan; Park, Jung Won; Park, Sang Woo

2013-01-01

To investigate light transmission and preference for six eye patches for occlusion therapy. Six patches were examined, including; Ortopad Fun Pack, Ortopad Flesh, Kawamoto A-1, Kawamoto A-2, 3M Opticlude, and Everade Eye Guard. The size and the presence of a light blocking pad of patches were investigated. The amount of light transmitted through the patches was evaluated, using a digital light meter and a model eye, in three different environments; indoors with fluorescent light, outdoors on a sunny day, and strong light from illuminator. After patching the normal eye, the flash visual evoked potential (VEP) was measured. Thirty patients with amblyopia or horizontal strabismus, who received occlusion therapy as initial treatment, were included. After using all six patches, patients completed a 7-item questionnaire regarding the patch preference for size, color and shape, adhesive power, pain with removal, skin irritation after removing patch, parent's preference and overall opinion. All patches had a light-blocking pad, except the 3M Nexcare. Ortopad had the strongest light blocking power in the three environments, and the 3M Nexcare had the weakest power. In flash VEP, Ortopad and Kawamoto patches showed flat, but 3M Nexcare and Everade Eye Guard showed normal response. There were significant preferential differences among the patches in all the items of the questionnaire (P<0.05). In comparison between the patches respectively, 3M Nexcare received the lowest satisfaction in pain when removing a patch and skin irritation after removing a patch. Kawamoto A-2 received the lowest score in the overall satisfaction. We found differences in the light-blocking power and in the preference of the various patches for the occlusion treatment. This is a pilot study regarding only characteristics and preferences of patches. Further clinical studies regarding the relationship between characteristics or preferences of patches and outcomes of occlusion treatment are needed.

[Impact of hypoglycemic episodes on nerves conduction and auditory and visual evoked potentials in children with type 1 diabetes].

PubMed

Wysocka-Mincewicz, Marta; Trippenbach-Dulska, Hanna; Emeryk-Szajewska, Barbara; Zakrzewska-Pniewska, Beata; Kochanek, Krzysztof; Pańkowska, Ewa

2007-01-01

Hypoglycemia is an acute disturbance of energy, especially impacting the central nervous system, but direct influence on peripheral nervous function is not detected. The aim of the study was to establish the influence of hypoglycemic moderate and severe episodes on the function of peripheral nerves, hearing and visual pathway. 97 children with type 1 diabetes (mean age 15.4+/-2.16 years, mean duration of diabetes 8.11+/-2.9 years, mean HbA1c 8,58+/-1.06%), at least 10 years old and with at least 3 years duration of diabetes, were included to study. Nerve conduction studies, visual (VEP) and auditory (ABR) evoked potentials were performed with standard surface stimulating and recording techniques. Moderate hypoglycemic episodes were defined as events of low glycemia requiring help of another person but without loss of consciousness and/or convulsions but recurrent frequently in at least one year. Severe hypoglycemia was defined as events with loss of consciousness and/or convulsions. Univariate ANOVA tests of significance or H Kruskal-Wallis test were used, depending on normality of distribution. The subgroups with a history of hypoglycemic episodes had significant delay in all conduction parameters in the sural nerve (amplitude p<0.05, sensory latency p<0.05, and velocity p<0.005) and in motor potential amplitude of tibial nerve (p<0.005). In ABR wave III latency and interval I-III in subgroups with episodes of hypoglycemia (p<0,05) were significantly prolonged. In analyses of VEP parameters no differences were detected. The study showed influence of hypoglycemic episodes on function of all sural nerve parameters and tibial motor amplitude, and in ABR on wave III and interval I-III. Frequent moderate hypoglycemic episodes were strong risk factors for damage of the peripheral and central nervous systems, comparable with impact of several severe hypoglycemias.

Quantitative comparisons of the acute neurotoxicity of toluene in rats and humans.

PubMed

Benignus, Vernon A; Boyes, William K; Kenyon, Elaina M; Bushnell, Philip J

2007-11-01

The behavioral and neurophysiological effects of acute exposure to toluene are the most thoroughly explored of all the hydrocarbon solvents. Behavioral effects have been experimentally studied in humans and other species, for example, rats. The existence of both rat and human dosimetric data offers the opportunity to quantitatively compare the relative sensitivity to acute toluene exposure. The purpose of this study was to fit dose-effect curves to existing data and to estimate the dose-equivalence equation (DEE) between rats and humans. The DEE gives the doses that produce the same magnitude of effect in the two species. Doses were brain concentrations of toluene estimated from physiologically based pharmacokinetic models. Human experiments measuring toluene effects on choice reaction time (CRT) were meta-analyzed. Rat studies employed various dependent variables: amplitude of visual-evoked potentials (VEPs), signal detection (SIGDET) accuracy (ACCU) and reaction time (RT), and escape-avoidance (ES-AV) behaviors. Comparison of dose-effect functions showed that human and rat sensitivity was practically the same for those two task regimens that exerted the least control over the behaviors being measured (VEP in rats and CRT in humans) and the sensitivity was progressively lower for SIGDET RT, SIGDET ACCU, and ES-AV behaviors in rats. These results suggested that the sensitivity to impairment by toluene depends on the strength of control over the measured behavior rather than on the species being tested. This interpretation suggests that (1) sensitivity to toluene would be equivalent in humans and rats if both species performed behaviors that were controlled to the same extent, (2) the most sensitive tests of neurobehavioral effects would be those in which least control is exerted on the behavior being measured, and (3) effects of toluene in humans may be estimated using the DEEs from rat studies despite differences in the amount of control exerted by the experimental regimen or differences in the behaviors under investigation.

Screening for Electrophysiological Abnormalities in Chronic Hepatitis C Infection: Peripheral Neuropathy and Optic Neuropathy.

PubMed

Köşkderelioğlu, Aslı; Ortan, Pınar; Ari, Alpay; Gedizlioğlu, Muhteşem

2016-03-01

To investigate the existence of peripheral and optic neuropathies in asymptomatic individuals with hepatitis C infection. Thirty consecutive patients who were followed in a hepatitis C outpatient clinic were recruited for electrophysiological evaluation together with 30 age- and gender-compatible healthy controls. All patients had a detailed neurological examination. The information regarding the disease duration and management with interferons were collected. Nerve conduction studies and visual evoked potentials (VEP) were recorded in all subjects. The results of the patient and control groups were statistically compared. Of the patients with hepatitis C infection, 16 were females and 14 males. The mean age was 57.5 years, and the average disease duration was 6.43 years. The P100 latencies in the patient group were within normal limits, while the amplitudes were meaningfully small by comparison with the controls. There were some abnormalities in the nerve conduction studies of 15 patients. Sensorial neuropathy was detected in two patients, sensorimotor polyneuropathy in four, carpal tunnel syndrome in seven, and carpal tunnel syndrome and sensorimotor polyneuropathy as comorbid states in another two patients. The nerve conduction studies and VEP parameters were entirely normal in the control group. Hepatitis C-related neurological abnormalities may occur both in the central and peripheral nervous system. Mononeuritis multiplex, sensorial axonal neuropathy, and multiple mononeuropathies are some of the presentations of the peripheral nervous system involvement. The mode of infection is considered to be via vasculitic mechanisms. In addition, optic neuropathy is a known complication of interferon treatment. Autoantibodies, cytokines, chemokines, and cryoglobulins are accused to play roles in the pathogenesis. In this study, we investigated the involvement of the peripheral nervous system and optic nerves in a group of patients with hepatitis C. The results were in favor of peripheral nerve injury of various types and optic neuropathy of the axonal type.

Evaluation of Different Antiretroviral Drug Protocols on Naturally Infected Feline Immunodeficiency Virus (FIV) Cats in the late Phase of the Asymptomatic Stage of Infection

PubMed Central

Gómez, Nélida V.; Fontanals, Adriana; Castillo, Víctor; Gisbert, María A.; Suraniti, Adriana; Mira, Graciela; Pisano, Paola B.

2012-01-01

The aim of this study was to evaluate the efficacy of the antiretrovirals: Zidovudine (ZDV) alone; ZDV + Recombinant Human Interferon-α (rHuIFN-α); ZDV + Lamivudine (3TC) and ZDV + valproic acid (Valp) on naturally feline immunodeficiency virus (FIV)-infected cats, in the late phase of the asymptomatic stage of infection. The follow-up was performed over one year, through clinical evaluation and the determination of viral loads and CD4+/CD8+ ratios. Neurological signs were studied by visual and auditory evoked potentials (VEP, AEP) and the responses were abnormal in 80% of the FIV-infected cats. After one year, an improvement in VEP and AEP was observed in the ZDV + Valp group and a worsening in the group receiving ZDV + rHuIFN-α. The CD4+/CD8+ ratio showed a significant increase (both intra and inter-groups) only in ZDV and ZDV + 3TC, between their pre-treatment and one year values, as well as among the other groups. Viral load only showed a significant decrease in ZDV and ZDV + 3TC groups, when comparing the values at one year of treatment vs. pre-treatment values and when the different groups were compared. In addition, the viral load decrease was significantly more pronounced in the ZDV + 3TC vs. ZDV group. We conclude that ZDV and ZDV + 3TC produce significant reductions in viral load and stimulate a recovery of the CD4+/CD8+ ratio, compared with the other protocols. It is clear that the addition of 3TC resulted in a greater reduction in viral load than use of ZDV as a single drug. Therefore, the combination ZDV + 3TC could be more effective than the sole use of ZDV. PMID:22816032

Long-Term Visuo-Gustatory Appetitive and Aversive Conditioning Potentiate Human Visual Evoked Potentials

PubMed Central

Christoffersen, Gert R. J.; Laugesen, Jakob L.; Møller, Per; Bredie, Wender L. P.; Schachtman, Todd R.; Liljendahl, Christina; Viemose, Ida

2017-01-01

Human recognition of foods and beverages are often based on visual cues associated with flavors. The dynamics of neurophysiological plasticity related to acquisition of such long-term associations has only recently become the target of investigation. In the present work, the effects of appetitive and aversive visuo-gustatory conditioning were studied with high density EEG-recordings focusing on late components in the visual evoked potentials (VEPs), specifically the N2-P3 waves. Unfamiliar images were paired with either a pleasant or an unpleasant juice and VEPs evoked by the images were compared before and 1 day after the pairings. In electrodes located over posterior visual cortex areas, the following changes were observed after conditioning: the amplitude from the N2-peak to the P3-peak increased and the N2 peak delay was reduced. The percentage increase of N2-to-P3 amplitudes was asymmetrically distributed over the posterior hemispheres despite the fact that the images were bilaterally symmetrical across the two visual hemifields. The percentage increases of N2-to-P3 amplitudes in each experimental subject correlated with the subject’s evaluation of positive or negative hedonic valences of the two juices. The results from 118 scalp electrodes gave surface maps of theta power distributions showing increased power over posterior visual areas after the pairings. Source current distributions calculated from swLORETA revealed that visual evoked currents rose as a result of conditioning in five cortical regions—from primary visual areas and into the inferior temporal gyrus (ITG). These learning-induced changes were seen after both appetitive and aversive training while a sham trained control group showed no changes. It is concluded that long-term visuo-gustatory conditioning potentiated the N2-P3 complex, and it is suggested that the changes are regulated by the perceived hedonic valence of the US. PMID:28983243

Acute effects of an organic solvent mixture on the human central nervous system.

PubMed

Muttray, Axel; Martus, P; Schachtrup, S; Müller, E; Mayer-Popken, O; Konietzko, J

2005-09-12

At workplaces, organic solvents are often used as mixtures. Nevertheless, there is limited knowledge of their acute effects on human central nervous system. Here we report the effects of a toluene-acetone mixture. In a parallel design, subgroups of 12 healthy men each were exposed to a mixture containing 25 ppm acetone and 250 ppm toluene or to air (control) in an exposure chamber for 4.5 hours. Concentrations corresponded to the German TLV (TRGS 403). Concentrations of toluene and acetone in venous blood were measured by headspace gas chromatography. Subjects were sedentary. The following tests were performed before and at the end of exposure: Questionnaires, simple reaction time, vigilance, quantitative analysis of EEG with open and closed eyes and during the Color Word Stress test, and visual evoked potentials (VEP). Blood levels were 0.14 (+/- 0.04 SD) mg toluene/l and 5.43 (+/- 1.37 SD) mg acetone/l at the end of solvent exposure. Scores of neurotoxic and irritating symptoms were not elevated during solvent exposure. Exposed subjects performed as well as control subjects on the simple reaction time test and on the vigilance test, neither reaction time nor number of hits differed significantly. A general linear model on log transformed spectral power values showed insignificant changes in EEG. In the alpha subset2-band an average reduction to 86 % was observed in exposed as compared to non exposed subjects with closed eyes, a reduction to 88 % in the theta-band with open eyes, and a reduction to 92 % in the theta-band during the Color Word Stress test. VEP P 100 latencies and amplitudes did not change. The mixture consisting of toluene and acetone did not cause any adverse acute effect. With respect to EEG data, possible subclinical effects on central nervous system cannot be excluded.

Sweep visually evoked potentials and visual findings in children with West syndrome.

PubMed

de Freitas Dotto, Patrícia; Cavascan, Nívea Nunes; Berezovsky, Adriana; Sacai, Paula Yuri; Rocha, Daniel Martins; Pereira, Josenilson Martins; Salomão, Solange Rios

2014-03-01

West syndrome (WS) is a type of early childhood epilepsy characterized by progressive neurological development deterioration that includes vision. To demonstrate the clinical importance of grating visual acuity thresholds (GVA) measurement by sweep visually evoked potentials technique (sweep-VEP) as a reliable tool for evaluation of the visual cortex status in WS children. This is a retrospective study of the best-corrected binocular GVA and ophthalmological features of WS children referred for the Laboratory of Clinical Electrophysiology of Vision of UNIFESP from 1998 to 2012 (Committee on Ethics in Research of UNIFESP n° 0349/08). The GVA deficit was calculated by subtracting binocular GVA score (logMAR units) of each patient from the median values of age norms from our own lab and classified as mild (0.1-0.39 logMAR), moderate (0.40-0.80 logMAR) or severe (>0.81 logMAR). Associated ophthalmological features were also described. Data from 30 WS children (age from 6 to 108 months, median = 14.5 months, mean ± SD = 22.0 ± 22.1 months; 19 male) were analyzed. The majority presented severe GVA deficit (0.15-1.44 logMAR; mean ± SD = 0.82 ± 0.32 logMAR; median = 0.82 logMAR), poor visual behavior, high prevalence of strabismus and great variability in ocular positioning. The GVA deficit did not vary according to gender (P = .8022), WS type (P = .908), birth age (P = .2881), perinatal oxygenation (P = .7692), visual behavior (P = .8789), ocular motility (P = .1821), nystagmus (P = .2868), risk of drug-induced retinopathy (P = .4632) and participation in early visual stimulation therapy (P = .9010). The sweep-VEP technique is a reliable tool to classify visual system impairment in WS children, in agreement with the poor visual behavior exhibited by them. Copyright © 2013 European Paediatric Neurology Society. Published by Elsevier Ltd. All rights reserved.

Effects of Maternal Ω-3 Supplementation on Fatty Acids and on Visual and Cognitive Development.

PubMed

Hurtado, Jose A; Iznaola, Carmen; Peña, Manuela; Ruíz, Josefa; Peña-Quintana, Luis; Kajarabille, Naroa; Rodriguez-Santana, Yessica; Sanjurjo, Pablo; Aldámiz-Echevarría, Luis; Ochoa, Julio; Lara-Villoslada, Federico

2015-10-01

The aim of the present study was to elucidate whether a dairy drink enriched with ω-3 long-chain polyunsaturated fatty acid (LC-PUFA) could have an impact on the lipid profile of the mother and the newborn, and also whether this intervention could affect the newborns' visual and cognitive development. A total of 110 pregnant women were randomly assigned to one of the following intervention groups: control group (n = 54), taking 400 mL/day of the control dairy drink, and supplemented group (fish oil [FO]) (n = 56), taking 400 mL/day of the fish oil-enriched dairy drink (including ∼400 mg eicosapentaenoic acid-docosahexaenoic acid [DHA]/day). During the study, the mothers' diets were supervised by a nutritionist to encourage compliance with present recommendations of FA intake. Blood fatty acid profiles were determined in the mother's (at enrollment, at delivery, and at 2.5 and 4 months) and newborn (at delivery and at 2.5 months) placenta and breast milk (colostrum and at 1, 2, and 4 months). Pattern reversal visual evoked potentials (VEPs) (at 2.5 and 7.5 months) and Bayley test (at 12 months) were recorded. DHA percentage was higher in plasma, erythrocyte membranes, and breast milk samples from the FO group. The ratio of nervonic acid was also higher in plasma and erythrocyte lipids of the mother and newborn's blood samples from the FO group. No differences were observed in the Bayley test. No differences were observed in VEPs between both groups. We observed a shorter latency, however, in the lower visual angle (7.5') in the boys of the supplemented group. Omega-3 LC-PUFA dietary supplement during pregnancy and lactation influenced the mother and newborn's fatty acid profile and nervonic acid content but did not show effects on visual and cognitive/psychomotor development.

Neurophysiological assessment of auditory, peripheral nerve, somatosensory, and visual system function after developmental exposure to gasoline, E15, and E85 vapors.

PubMed

Herr, David W; Freeborn, Danielle L; Degn, Laura; Martin, Sheppard A; Ortenzio, Jayna; Pantlin, Lara; Hamm, Charles W; Boyes, William K

2016-01-01

The use of gasolines blended with a range of ethanol concentrations may result in inhalation of vapors containing a variable combination of ethanol with other volatile gasoline constituents. The possibility of exposure and potential interactions between vapor constituents suggests the need to evaluate the possible risks of this complex mixture. Previously we evaluated the effects of developmental exposure to ethanol vapors on neurophysiological measures of sensory function as a component of a larger project evaluating developmental ethanol toxicity. Here we report an evaluation using the same battery of sensory function testing in offspring of pregnant dams exposed during gestation to condensed vapors of gasoline (E0), gasoline blended with 15% ethanol (E15) or gasoline blended with 85% ethanol (E85). Pregnant Long-Evans rats were exposed to target concentrations 0, 3000, 6000, or 9000 ppm total hydrocarbon vapors for 6.5h/day over GD9 - GD20. Sensory evaluations of male offspring began as adults. The electrophysiological testing battery included tests of: peripheral nerve (compound action potentials, nerve conduction velocity [NCV]), somatosensory (cortical and cerebellar evoked potentials), auditory (brainstem auditory evoked responses), and visual functions. Visual function assessment included pattern elicited visual evoked potentials (VEP), VEP contrast sensitivity, dark-adapted (scotopic) electroretinograms (ERGs), light-adapted (photopic) ERGs, and green flicker ERGs. The results included sporadic statistically significant effects, but the observations were not consistently concentration-related and appeared to be statistical Type 1 errors related to multiple dependent measures evaluated. The exposure concentrations were much higher than can be reasonably expected from typical exposures to the general population during refueling or other common exposure situations. Overall the results indicate that gestational exposure of male rats to ethanol/gasoline vapor combinations did not cause detectable changes in peripheral nerve, somatosensory, auditory, or visual function when the offspring were assessed as adults. Published by Elsevier Inc.

Visual Evoked Potentials in Infants With Diffuse Periventricular Leukomalacia.

PubMed

Carbajal-Valenzuela, Cintli Carolina; Santiago-Rodríguez, Efraín; Harmony, Thalía; Fernández-Bouzas, Antonio

2014-10-01

Periventricular leukomalacia (PVL) is characterized by necrosis of the cerebral white matter in the dorsolateral portions of the lateral ventricles. PVL causes motor, sensory, and cognitive deficits. The aim of this study was to analyze the conduction characteristics of the visual pathway in infants with diffuse PVL using visual evoked potentials (VEPs). We studied 11 healthy infants (mean age 3.3 ± 1.3 months) and 17 with diffuse PVL (mean age 2.9 ± 0.8 months and mean gestational age 31.9 ± 3.1 weeks). The N75, P100, and N135 wave latencies; the interwave N75-P100 and P100-N135 latencies; and the N75-P100 and P100-N135 amplitudes were measured in the occipital leads. VEPs were recorded during binocular stimulation at an angle of 120' from the Fz-Oz lead. Healthy children had mean N75, P100, and N135 wave latencies of 84.4 ± 5.8, 143.4 ± 30.6 and 222.9 ± 40.4 ms, respectively. The mean interwave N75-P100 and P100-N135 latencies were 59.0 ± 28.6 and 79.5 ± 13.6 ms, respectively. Compared with the healthy group, infants with PVL had longer N75 and N135 latencies at 92.3 ± 15.3 (P = .05) and 265.0 ms ± 60.3 (P = .05), respectively. The interwave latency P100-N135 (105.5 ± 29.1 ms; P = .017) was longer in children with PVL than in healthy infants. Infants with diffuse PVL had mild alterations in their N75, P100 and, particularly, their N135 latencies. These increases in P100-N135 interwave latencies could be because of damage to the geniculocortical pathways and V2-V3 networks. © EEG and Clinical Neuroscience Society (ECNS) 2014.

A new method for species identification via protein-coding and non-coding DNA barcodes by combining machine learning with bioinformatic methods.

PubMed

Zhang, Ai-bing; Feng, Jie; Ward, Robert D; Wan, Ping; Gao, Qiang; Wu, Jun; Zhao, Wei-zhong

2012-01-01

Species identification via DNA barcodes is contributing greatly to current bioinventory efforts. The initial, and widely accepted, proposal was to use the protein-coding cytochrome c oxidase subunit I (COI) region as the standard barcode for animals, but recently non-coding internal transcribed spacer (ITS) genes have been proposed as candidate barcodes for both animals and plants. However, achieving a robust alignment for non-coding regions can be problematic. Here we propose two new methods (DV-RBF and FJ-RBF) to address this issue for species assignment by both coding and non-coding sequences that take advantage of the power of machine learning and bioinformatics. We demonstrate the value of the new methods with four empirical datasets, two representing typical protein-coding COI barcode datasets (neotropical bats and marine fish) and two representing non-coding ITS barcodes (rust fungi and brown algae). Using two random sub-sampling approaches, we demonstrate that the new methods significantly outperformed existing Neighbor-joining (NJ) and Maximum likelihood (ML) methods for both coding and non-coding barcodes when there was complete species coverage in the reference dataset. The new methods also out-performed NJ and ML methods for non-coding sequences in circumstances of potentially incomplete species coverage, although then the NJ and ML methods performed slightly better than the new methods for protein-coding barcodes. A 100% success rate of species identification was achieved with the two new methods for 4,122 bat queries and 5,134 fish queries using COI barcodes, with 95% confidence intervals (CI) of 99.75-100%. The new methods also obtained a 96.29% success rate (95%CI: 91.62-98.40%) for 484 rust fungi queries and a 98.50% success rate (95%CI: 96.60-99.37%) for 1094 brown algae queries, both using ITS barcodes.

Inclusion of Visually Impaired in the School Programme Scheduled Visit of the Museu de Astronomia e Ciências Afins (MAST). (Breton Title: Inclusão de Deficientes Visuais no Programa de Visita Escolar Programada do Museu de Astronomia e Ciências Afins (MAST).) Inclusión de Discapacitados Visuales en el Programa Escolar Programado del Museo de Astronomía y Ciencias Afines (MAST)

NASA Astrophysics Data System (ADS)

de Oliveira Gonçalves, Carla; da Conceição Barbosa-Lima, Maria

2013-07-01

Inclusive Education in Brazil, contemplated in the 1988 Constitution and in the Law of Guidelines and Bases of National Education (9.394/96) highlights the importance and urgency of promoting inclusive education as a formative element of nationality. Inclusive Education refers to all people who are struggling in school. Inclusion should be in all educational institutions (formal and informal). Our goal in the graduation final task was to report the experience of mediation to visually impaired students of the Instituto Benjamin Constant (IBC) at the Museu de Astronomia e Ciências Afins (MAST), and also suggest some modifications and present new proposals for the School Visit Program (VEP) through a specially constructed apparatus, where the sky can be sensed near the latitude of Rio de Janeiro. A educação inclusiva no Brasil, contemplada na Constituição de 1988 e a Lei de Diretrizes e Bases da Educação Nacional (9.394/96), destaca a importância e urgência de se promover a inclusão escolar como elemento formador da nacionalidade. A educação inclusiva diz respeito a todas as pessoas que enfrentam dificuldades na escola. A inclusão deve estar em todas as instituições educacionais (formais e não formais). Nosso objetivo, no trabalho de final de curso de licenciatura, foi apresentar o relato de experiência de mediação aos alunos deficientes visuais do Instituto Benjamin Constant (IBC) no Museu de Astronomia e Ciências Afins (MAST), as modificações e novas propostas para o Programa de Visita Escolar Programada (VEP) através de um aparelho especialmente construído onde se pode perceber o céu na latitude próxima a do Rio de Janeiro. La educación inclusiva en el Brasil, contemplada en la Constitución de 1988 y en la Ley de Directrices y Bases de la Educación Nacional (9.394/96), destaca la importancia y la urgencia de promover la inclusión escolar como elemento formador de la nacionalidad. La educación inclusiva se refiere a todas las personas que enfrentan dificultades en la escuela. La inclusión debe estar en todas las instituciones educacionales (formales o no). Nuestro objetivo en el trabajo de final de curso de licenciatura, fue el de presentar un relato de la experiencia de mediación a los alumnos con deficiencias visuales del Instituto Benjamin Constant (IBC) en el Museo de Astronomía y Ciencias Afines (MAST) y las modificaciones y nuevas propuestas para el Programa de Visita Escolar Programada (VEP) a través de un aparato especialmente construido con el cual se puede percibir el cielo en una latitud próxima a la de Rio de Janeiro.

Coding For Compression Of Low-Entropy Data

NASA Technical Reports Server (NTRS)

Yeh, Pen-Shu

1994-01-01

Improved method of encoding digital data provides for efficient lossless compression of partially or even mostly redundant data from low-information-content source. Method of coding implemented in relatively simple, high-speed arithmetic and logic circuits. Also increases coding efficiency beyond that of established Huffman coding method in that average number of bits per code symbol can be less than 1, which is the lower bound for Huffman code.

P-Code-Enhanced Encryption-Mode Processing of GPS Signals

NASA Technical Reports Server (NTRS)

Young, Lawrence; Meehan, Thomas; Thomas, Jess B.

2003-01-01

A method of processing signals in a Global Positioning System (GPS) receiver has been invented to enable the receiver to recover some of the information that is otherwise lost when GPS signals are encrypted at the transmitters. The need for this method arises because, at the option of the military, precision GPS code (P-code) is sometimes encrypted by a secret binary code, denoted the A code. Authorized users can recover the full signal with knowledge of the A-code. However, even in the absence of knowledge of the A-code, one can track the encrypted signal by use of an estimate of the A-code. The present invention is a method of making and using such an estimate. In comparison with prior such methods, this method makes it possible to recover more of the lost information and obtain greater accuracy.

Constructing LDPC Codes from Loop-Free Encoding Modules

NASA Technical Reports Server (NTRS)

Divsalar, Dariush; Dolinar, Samuel; Jones, Christopher; Thorpe, Jeremy; Andrews, Kenneth

2009-01-01

A method of constructing certain low-density parity-check (LDPC) codes by use of relatively simple loop-free coding modules has been developed. The subclasses of LDPC codes to which the method applies includes accumulate-repeat-accumulate (ARA) codes, accumulate-repeat-check-accumulate codes, and the codes described in Accumulate-Repeat-Accumulate-Accumulate Codes (NPO-41305), NASA Tech Briefs, Vol. 31, No. 9 (September 2007), page 90. All of the affected codes can be characterized as serial/parallel (hybrid) concatenations of such relatively simple modules as accumulators, repetition codes, differentiators, and punctured single-parity check codes. These are error-correcting codes suitable for use in a variety of wireless data-communication systems that include noisy channels. These codes can also be characterized as hybrid turbolike codes that have projected graph or protograph representations (for example see figure); these characteristics make it possible to design high-speed iterative decoders that utilize belief-propagation algorithms. The present method comprises two related submethods for constructing LDPC codes from simple loop-free modules with circulant permutations. The first submethod is an iterative encoding method based on the erasure-decoding algorithm. The computations required by this method are well organized because they involve a parity-check matrix having a block-circulant structure. The second submethod involves the use of block-circulant generator matrices. The encoders of this method are very similar to those of recursive convolutional codes. Some encoders according to this second submethod have been implemented in a small field-programmable gate array that operates at a speed of 100 megasymbols per second. By use of density evolution (a computational- simulation technique for analyzing performances of LDPC codes), it has been shown through some examples that as the block size goes to infinity, low iterative decoding thresholds close to channel capacity limits can be achieved for the codes of the type in question having low maximum variable node degrees. The decoding thresholds in these examples are lower than those of the best-known unstructured irregular LDPC codes constrained to have the same maximum node degrees. Furthermore, the present method enables the construction of codes of any desired rate with thresholds that stay uniformly close to their respective channel capacity thresholds.

Preliminary study on combined pharmacological and laser treatment in optic pit serous maculopathy after literature review.

PubMed

Nebbioso, M; Dapoto, L; Lenarduzzi, F; Belcaro, G; Malagola, R

2012-12-01

The pit of the optic nerve head (ON) is a rare congenital defect that sometimes presents itself with a maculopathy of various neuroretinal layers for unknown reason. This study was focused, before and after pharmacological and parasurgical treatment, on the structural and functional visual assessment in a patient with optic pit maculopathy (OPM). In order to achieve this the latest generation of hi-tech diagnostic tests were used, such as Spectral-Domain Optical Coherence Tomography (SD-OCT), Visual Evoked Potentials (VEP), full-field Electroretinography (ERG), multifocal ERG (mfERG), Microperimetry (MP-1), Standard Automated Perimetry (SAP), Fluorescein Angiography (FA) and Indocyanine Green Angiography (ICG). The research was conducted through a review of past and recent literature.

Evaluation of a visual layering methodology for colour coding control room displays.

PubMed

Van Laar, Darren; Deshe, Ofer

2002-07-01

Eighteen people participated in an experiment in which they were asked to search for targets on control room like displays which had been produced using three different coding methods. The monochrome coding method displayed the information in black and white only, the maximally discriminable method contained colours chosen for their high perceptual discriminability, the visual layers method contained colours developed from psychological and cartographic principles which grouped information into a perceptual hierarchy. The visual layers method produced significantly faster search times than the other two coding methods which did not differ significantly from each other. Search time also differed significantly for presentation order and for the method x order interaction. There was no significant difference between the methods in the number of errors made. Participants clearly preferred the visual layers coding method. Proposals are made for the design of experiments to further test and develop the visual layers colour coding methodology.

A progressive data compression scheme based upon adaptive transform coding: Mixture block coding of natural images

NASA Technical Reports Server (NTRS)

Rost, Martin C.; Sayood, Khalid

1991-01-01

A method for efficiently coding natural images using a vector-quantized variable-blocksized transform source coder is presented. The method, mixture block coding (MBC), incorporates variable-rate coding by using a mixture of discrete cosine transform (DCT) source coders. Which coders are selected to code any given image region is made through a threshold driven distortion criterion. In this paper, MBC is used in two different applications. The base method is concerned with single-pass low-rate image data compression. The second is a natural extension of the base method which allows for low-rate progressive transmission (PT). Since the base method adapts easily to progressive coding, it offers the aesthetic advantage of progressive coding without incorporating extensive channel overhead. Image compression rates of approximately 0.5 bit/pel are demonstrated for both monochrome and color images.

Local statistics adaptive entropy coding method for the improvement of H.26L VLC coding

NASA Astrophysics Data System (ADS)

Yoo, Kook-yeol; Kim, Jong D.; Choi, Byung-Sun; Lee, Yung Lyul

2000-05-01

In this paper, we propose an adaptive entropy coding method to improve the VLC coding efficiency of H.26L TML-1 codec. First of all, we will show that the VLC coding presented in TML-1 does not satisfy the sibling property of entropy coding. Then, we will modify the coding method into the local statistics adaptive one to satisfy the property. The proposed method based on the local symbol statistics dynamically changes the mapping relationship between symbol and bit pattern in the VLC table according to sibling property. Note that the codewords in the VLC table of TML-1 codec is not changed. Since this changed mapping relationship also derived in the decoder side by using the decoded symbols, the proposed VLC coding method does not require any overhead information. The simulation results show that the proposed method gives about 30% and 37% reduction in average bit rate for MB type and CBP information, respectively.

A method for modeling co-occurrence propensity of clinical codes with application to ICD-10-PCS auto-coding.

PubMed

Subotin, Michael; Davis, Anthony R

2016-09-01

Natural language processing methods for medical auto-coding, or automatic generation of medical billing codes from electronic health records, generally assign each code independently of the others. They may thus assign codes for closely related procedures or diagnoses to the same document, even when they do not tend to occur together in practice, simply because the right choice can be difficult to infer from the clinical narrative. We propose a method that injects awareness of the propensities for code co-occurrence into this process. First, a model is trained to estimate the conditional probability that one code is assigned by a human coder, given than another code is known to have been assigned to the same document. Then, at runtime, an iterative algorithm is used to apply this model to the output of an existing statistical auto-coder to modify the confidence scores of the codes. We tested this method in combination with a primary auto-coder for International Statistical Classification of Diseases-10 procedure codes, achieving a 12% relative improvement in F-score over the primary auto-coder baseline. The proposed method can be used, with appropriate features, in combination with any auto-coder that generates codes with different levels of confidence. The promising results obtained for International Statistical Classification of Diseases-10 procedure codes suggest that the proposed method may have wider applications in auto-coding. © The Author 2016. Published by Oxford University Press on behalf of the American Medical Informatics Association. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

fMRI and EEG responses to periodic visual stimulation.

PubMed

Guy, C N; ffytche, D H; Brovelli, A; Chumillas, J

1999-08-01

EEG/VEP and fMRI responses to periodic visual stimulation are reported. The purpose of these experiments was to look for similar patterns in the time series produced by each method to help understand the relationship between the two. The stimulation protocol was the same for both sets of experiments and consisted of five complete cycles of checkerboard pattern reversal at 1.87 Hz for 30 s followed by 30 s of a stationary checkerboard. The fMRI data was analyzed using standard methods, while the EEG was analyzed with a new measurement of activation-the VEPEG. Both VEPEG and fMRI time series contain the fundamental frequency of the stimulus and quasi harmonic components-an unexplained double frequency commonly found in fMRI data. These results have prompted a reappraisal of the methods for analyzing fMRI data and have suggested a connection between our findings and much older published invasive electrophysiological measurements of blood flow and the partial pressures of oxygen and carbon dioxide. Overall our new analysis suggests that fMRI signals are strongly dependant on hydraulic blood flow effects. We distinguish three categories of fMRI signal corresponding to: focal activated regions of brain tissue; diffuse nonspecific regions of steal; and major cerebral vessels of arterial supply or venous drainage. Each category of signal has its own finger print in frequency, amplitude, and phase. Finally, we put forward the hypothesis that modulations in blood flow are not only the consequence but are also the cause of modulations in functional activity. Copyright 1999 Academic Press.

Comparison of two methods of MMPI-2 profile classification.

PubMed

Munley, P H; Germain, J M

2000-10-01

The present study investigated the extent of agreement of the highest scale method and the best-fit method in matching MMPI-2 profiles to database code-type profiles and considered profile characteristics that may relate to agreement or disagreement of code-type matches by these two methods. A sample of 519 MMPI-2 profiles that had been classified into database profile code types by these two methods was studied. Resulting code-type matches were classified into three groups: identical (30%), similar (39%), and different (31%), and the profile characteristics of profile elevation, dispersion, and profile code-type definition were studied. Profile code-type definition was significantly different across the three groups with identical and similar match profile groups showing greater profile code-type definition and the different group consisting of profiles that were less well-defined.

A novel construction method of QC-LDPC codes based on the subgroup of the finite field multiplicative group for optical transmission systems

NASA Astrophysics Data System (ADS)

Yuan, Jian-guo; Zhou, Guang-xiang; Gao, Wen-chun; Wang, Yong; Lin, Jin-zhao; Pang, Yu

2016-01-01

According to the requirements of the increasing development for optical transmission systems, a novel construction method of quasi-cyclic low-density parity-check (QC-LDPC) codes based on the subgroup of the finite field multiplicative group is proposed. Furthermore, this construction method can effectively avoid the girth-4 phenomena and has the advantages such as simpler construction, easier implementation, lower encoding/decoding complexity, better girth properties and more flexible adjustment for the code length and code rate. The simulation results show that the error correction performance of the QC-LDPC(3 780,3 540) code with the code rate of 93.7% constructed by this proposed method is excellent, its net coding gain is respectively 0.3 dB, 0.55 dB, 1.4 dB and 1.98 dB higher than those of the QC-LDPC(5 334,4 962) code constructed by the method based on the inverse element characteristics in the finite field multiplicative group, the SCG-LDPC(3 969,3 720) code constructed by the systematically constructed Gallager (SCG) random construction method, the LDPC(32 640,30 592) code in ITU-T G.975.1 and the classic RS(255,239) code which is widely used in optical transmission systems in ITU-T G.975 at the bit error rate ( BER) of 10-7. Therefore, the constructed QC-LDPC(3 780,3 540) code is more suitable for optical transmission systems.

Research on pre-processing of QR Code

NASA Astrophysics Data System (ADS)

Sun, Haixing; Xia, Haojie; Dong, Ning

2013-10-01

QR code encodes many kinds of information because of its advantages: large storage capacity, high reliability, full arrange of utter-high-speed reading, small printing size and high-efficient representation of Chinese characters, etc. In order to obtain the clearer binarization image from complex background, and improve the recognition rate of QR code, this paper researches on pre-processing methods of QR code (Quick Response Code), and shows algorithms and results of image pre-processing for QR code recognition. Improve the conventional method by changing the Souvola's adaptive text recognition method. Additionally, introduce the QR code Extraction which adapts to different image size, flexible image correction approach, and improve the efficiency and accuracy of QR code image processing.

Advancing methods for reliably assessing motivational interviewing fidelity using the Motivational Interviewing Skills Code

PubMed Central

Lord, Sarah Peregrine; Can, Doğan; Yi, Michael; Marin, Rebeca; Dunn, Christopher W.; Imel, Zac E.; Georgiou, Panayiotis; Narayanan, Shrikanth; Steyvers, Mark; Atkins, David C.

2014-01-01

The current paper presents novel methods for collecting MISC data and accurately assessing reliability of behavior codes at the level of the utterance. The MISC 2.1 was used to rate MI interviews from five randomized trials targeting alcohol and drug use. Sessions were coded at the utterance-level. Utterance-based coding reliability was estimated using three methods and compared to traditional reliability estimates of session tallies. Session-level reliability was generally higher compared to reliability using utterance-based codes, suggesting that typical methods for MISC reliability may be biased. These novel methods in MI fidelity data collection and reliability assessment provided rich data for therapist feedback and further analyses. Beyond implications for fidelity coding, utterance-level coding schemes may elucidate important elements in the counselor-client interaction that could inform theories of change and the practice of MI. PMID:25242192

Advancing methods for reliably assessing motivational interviewing fidelity using the motivational interviewing skills code.

PubMed

Lord, Sarah Peregrine; Can, Doğan; Yi, Michael; Marin, Rebeca; Dunn, Christopher W; Imel, Zac E; Georgiou, Panayiotis; Narayanan, Shrikanth; Steyvers, Mark; Atkins, David C

2015-02-01

The current paper presents novel methods for collecting MISC data and accurately assessing reliability of behavior codes at the level of the utterance. The MISC 2.1 was used to rate MI interviews from five randomized trials targeting alcohol and drug use. Sessions were coded at the utterance-level. Utterance-based coding reliability was estimated using three methods and compared to traditional reliability estimates of session tallies. Session-level reliability was generally higher compared to reliability using utterance-based codes, suggesting that typical methods for MISC reliability may be biased. These novel methods in MI fidelity data collection and reliability assessment provided rich data for therapist feedback and further analyses. Beyond implications for fidelity coding, utterance-level coding schemes may elucidate important elements in the counselor-client interaction that could inform theories of change and the practice of MI. Copyright © 2015 Elsevier Inc. All rights reserved.

Detecting the borders between coding and non-coding DNA regions in prokaryotes based on recursive segmentation and nucleotide doublets statistics

PubMed Central

2012-01-01

Background Detecting the borders between coding and non-coding regions is an essential step in the genome annotation. And information entropy measures are useful for describing the signals in genome sequence. However, the accuracies of previous methods of finding borders based on entropy segmentation method still need to be improved. Methods In this study, we first applied a new recursive entropic segmentation method on DNA sequences to get preliminary significant cuts. A 22-symbol alphabet is used to capture the differential composition of nucleotide doublets and stop codon patterns along three phases in both DNA strands. This process requires no prior training datasets. Results Comparing with the previous segmentation methods, the experimental results on three bacteria genomes, Rickettsia prowazekii, Borrelia burgdorferi and E.coli, show that our approach improves the accuracy for finding the borders between coding and non-coding regions in DNA sequences. Conclusions This paper presents a new segmentation method in prokaryotes based on Jensen-Rényi divergence with a 22-symbol alphabet. For three bacteria genomes, comparing to A12_JR method, our method raised the accuracy of finding the borders between protein coding and non-coding regions in DNA sequences. PMID:23282225

Automated encoding of clinical documents based on natural language processing.

PubMed

Friedman, Carol; Shagina, Lyudmila; Lussier, Yves; Hripcsak, George

2004-01-01

The aim of this study was to develop a method based on natural language processing (NLP) that automatically maps an entire clinical document to codes with modifiers and to quantitatively evaluate the method. An existing NLP system, MedLEE, was adapted to automatically generate codes. The method involves matching of structured output generated by MedLEE consisting of findings and modifiers to obtain the most specific code. Recall and precision applied to Unified Medical Language System (UMLS) coding were evaluated in two separate studies. Recall was measured using a test set of 150 randomly selected sentences, which were processed using MedLEE. Results were compared with a reference standard determined manually by seven experts. Precision was measured using a second test set of 150 randomly selected sentences from which UMLS codes were automatically generated by the method and then validated by experts. Recall of the system for UMLS coding of all terms was .77 (95% CI.72-.81), and for coding terms that had corresponding UMLS codes recall was .83 (.79-.87). Recall of the system for extracting all terms was .84 (.81-.88). Recall of the experts ranged from .69 to .91 for extracting terms. The precision of the system was .89 (.87-.91), and precision of the experts ranged from .61 to .91. Extraction of relevant clinical information and UMLS coding were accomplished using a method based on NLP. The method appeared to be comparable to or better than six experts. The advantage of the method is that it maps text to codes along with other related information, rendering the coded output suitable for effective retrieval.

Improved lossless intra coding for H.264/MPEG-4 AVC.

PubMed

Lee, Yung-Lyul; Han, Ki-Hun; Sullivan, Gary J

2006-09-01

A new lossless intra coding method based on sample-by-sample differential pulse code modulation (DPCM) is presented as an enhancement of the H.264/MPEG-4 AVC standard. The H.264/AVC design includes a multidirectional spatial prediction method to reduce spatial redundancy by using neighboring samples as a prediction for the samples in a block of data to be encoded. In the new lossless intra coding method, the spatial prediction is performed based on samplewise DPCM instead of in the block-based manner used in the current H.264/AVC standard, while the block structure is retained for the residual difference entropy coding process. We show that the new method, based on samplewise DPCM, does not have a major complexity penalty, despite its apparent pipeline dependencies. Experiments show that the new lossless intra coding method reduces the bit rate by approximately 12% in comparison with the lossless intra coding method previously included in the H.264/AVC standard. As a result, the new method is currently being adopted into the H.264/AVC standard in a new enhancement project.

Effective Identification of Similar Patients Through Sequential Matching over ICD Code Embedding.

PubMed

Nguyen, Dang; Luo, Wei; Venkatesh, Svetha; Phung, Dinh

2018-04-11

Evidence-based medicine often involves the identification of patients with similar conditions, which are often captured in ICD (International Classification of Diseases (World Health Organization 2013)) code sequences. With no satisfying prior solutions for matching ICD-10 code sequences, this paper presents a method which effectively captures the clinical similarity among routine patients who have multiple comorbidities and complex care needs. Our method leverages the recent progress in representation learning of individual ICD-10 codes, and it explicitly uses the sequential order of codes for matching. Empirical evaluation on a state-wide cancer data collection shows that our proposed method achieves significantly higher matching performance compared with state-of-the-art methods ignoring the sequential order. Our method better identifies similar patients in a number of clinical outcomes including readmission and mortality outlook. Although this paper focuses on ICD-10 diagnosis code sequences, our method can be adapted to work with other codified sequence data.

The impact of three discharge coding methods on the accuracy of diagnostic coding and hospital reimbursement for inpatient medical care.

PubMed

Tsopra, Rosy; Peckham, Daniel; Beirne, Paul; Rodger, Kirsty; Callister, Matthew; White, Helen; Jais, Jean-Philippe; Ghosh, Dipansu; Whitaker, Paul; Clifton, Ian J; Wyatt, Jeremy C

2018-07-01

Coding of diagnoses is important for patient care, hospital management and research. However coding accuracy is often poor and may reflect methods of coding. This study investigates the impact of three alternative coding methods on the inaccuracy of diagnosis codes and hospital reimbursement. Comparisons of coding inaccuracy were made between a list of coded diagnoses obtained by a coder using (i)the discharge summary alone, (ii)case notes and discharge summary, and (iii)discharge summary with the addition of medical input. For each method, inaccuracy was determined for the primary, secondary diagnoses, Healthcare Resource Group (HRG) and estimated hospital reimbursement. These data were then compared with a gold standard derived by a consultant and coder. 107 consecutive patient discharges were analysed. Inaccuracy of diagnosis codes was highest when a coder used the discharge summary alone, and decreased significantly when the coder used the case notes (70% vs 58% respectively, p < 0.0001) or coded from the discharge summary with medical support (70% vs 60% respectively, p < 0.0001). When compared with the gold standard, the percentage of incorrect HRGs was 42% for discharge summary alone, 31% for coding with case notes, and 35% for coding with medical support. The three coding methods resulted in an annual estimated loss of hospital remuneration of between £1.8 M and £16.5 M. The accuracy of diagnosis codes and percentage of correct HRGs improved when coders used either case notes or medical support in addition to the discharge summary. Further emphasis needs to be placed on improving the standard of information recorded in discharge summaries. Copyright © 2018 Elsevier B.V. All rights reserved.

The Plasma Simulation Code: A modern particle-in-cell code with patch-based load-balancing

NASA Astrophysics Data System (ADS)

Germaschewski, Kai; Fox, William; Abbott, Stephen; Ahmadi, Narges; Maynard, Kristofor; Wang, Liang; Ruhl, Hartmut; Bhattacharjee, Amitava

2016-08-01

This work describes the Plasma Simulation Code (PSC), an explicit, electromagnetic particle-in-cell code with support for different order particle shape functions. We review the basic components of the particle-in-cell method as well as the computational architecture of the PSC code that allows support for modular algorithms and data structure in the code. We then describe and analyze in detail a distinguishing feature of PSC: patch-based load balancing using space-filling curves which is shown to lead to major efficiency gains over unbalanced methods and a previously used simpler balancing method.

Methods for Ensuring High Quality of Coding of Cause of Death. The Mortality Register to Follow Southern Urals Populations Exposed to Radiation.

PubMed

Startsev, N; Dimov, P; Grosche, B; Tretyakov, F; Schüz, J; Akleyev, A

2015-01-01

To follow up populations exposed to several radiation accidents in the Southern Urals, a cause-of-death registry was established at the Urals Center capturing deaths in the Chelyabinsk, Kurgan and Sverdlovsk region since 1950. When registering deaths over such a long time period, quality measures need to be in place to maintain quality and reduce the impact of individual coders as well as quality changes in death certificates. To ensure the uniformity of coding, a method for semi-automatic coding was developed, which is described here. Briefly, the method is based on a dynamic thesaurus, database-supported coding and parallel coding by two different individuals. A comparison of the proposed method for organizing the coding process with the common procedure of coding showed good agreement, with, at the end of the coding process, 70  - 90% agreement for the three-digit ICD -9 rubrics. The semi-automatic method ensures a sufficiently high quality of coding by at the same time providing an opportunity to reduce the labor intensity inherent in the creation of large-volume cause-of-death registries.

A study of transonic aerodynamic analysis methods for use with a hypersonic aircraft synthesis code

NASA Technical Reports Server (NTRS)

Sandlin, Doral R.; Davis, Paul Christopher

1992-01-01

A means of performing routine transonic lift, drag, and moment analyses on hypersonic all-body and wing-body configurations were studied. The analysis method is to be used in conjunction with the Hypersonic Vehicle Optimization Code (HAVOC). A review of existing techniques is presented, after which three methods, chosen to represent a spectrum of capabilities, are tested and the results are compared with experimental data. The three methods consist of a wave drag code, a full potential code, and a Navier-Stokes code. The wave drag code, representing the empirical approach, has very fast CPU times, but very limited and sporadic results. The full potential code provides results which compare favorably to the wind tunnel data, but with a dramatic increase in computational time. Even more extreme is the Navier-Stokes code, which provides the most favorable and complete results, but with a very large turnaround time. The full potential code, TRANAIR, is used for additional analyses, because of the superior results it can provide over empirical and semi-empirical methods, and because of its automated grid generation. TRANAIR analyses include an all body hypersonic cruise configuration and an oblique flying wing supersonic transport.

Management: Department of the Army Productivity Improvement Program

DTIC Science & Technology

1982-08-01

VEPs will submit semi-annually to HQDA ( DACA -MP) WASH DC 20310 a statistical summary of VE actions (RCS DD- I&L (SA&A) 1138) in the format shown in...A r m y c o m m a n d s / s e p a r a t e a g e n c i e s w i l l furnish one copy of each to the Comptrol- ler of the Army, HQDA, ATTN: DACA - MP...d e d C h a n g e s t o P u b l i c a t i o n s a n d Blank Forms) direct to HQDA ( DACA - RPM) WASH DC 20310. D i s t r i b u t i o n . A c t i v e A

Quantized phase coding and connected region labeling for absolute phase retrieval.

PubMed

Chen, Xiangcheng; Wang, Yuwei; Wang, Yajun; Ma, Mengchao; Zeng, Chunnian

2016-12-12

This paper proposes an absolute phase retrieval method for complex object measurement based on quantized phase-coding and connected region labeling. A specific code sequence is embedded into quantized phase of three coded fringes. Connected regions of different codes are labeled and assigned with 3-digit-codes combining the current period and its neighbors. Wrapped phase, more than 36 periods, can be restored with reference to the code sequence. Experimental results verify the capability of the proposed method to measure multiple isolated objects.

Interactive QR code beautification with full background image embedding

NASA Astrophysics Data System (ADS)

Lin, Lijian; Wu, Song; Liu, Sijiang; Jiang, Bo

2017-06-01

QR (Quick Response) code is a kind of two dimensional barcode that was first developed in automotive industry. Nowadays, QR code has been widely used in commercial applications like product promotion, mobile payment, product information management, etc. Traditional QR codes in accordance with the international standard are reliable and fast to decode, but are lack of aesthetic appearance to demonstrate visual information to customers. In this work, we present a novel interactive method to generate aesthetic QR code. By given information to be encoded and an image to be decorated as full QR code background, our method accepts interactive user's strokes as hints to remove undesired parts of QR code modules based on the support of QR code error correction mechanism and background color thresholds. Compared to previous approaches, our method follows the intention of the QR code designer, thus can achieve more user pleasant result, while keeping high machine readability.

Accuracy of coded excitation methods for measuring the time of flight: Application to ultrasonic characterization of wood samples.

PubMed

Lasaygues, Philippe; Arciniegas, Andres; Espinosa, Luis; Prieto, Flavio; Brancheriau, Loïc

2018-05-26

Ultrasound computed tomography (USCT) using the transmission mode is a way to detect and assess the extent of decay in wood structures. The resolution of the ultrasonic image is closely related to the different anatomical features of wood. The complexity of the wave propagation process generates complex signals consisting of several wave packets with different signatures. Wave paths, depth dependencies, wave velocities or attenuations are often difficult to interpret. For this kind of assessment, the focus is generally on signal pre-processing. Several approaches have been used so far including filtering, spectrum analysis and a method involving deconvolution using a characteristic transfer function of the experimental device. However, all these approaches may be too sophisticated and/or unstable. The alternative methods proposed in this work are based on coded excitation, which makes it possible to process both local and general information available such as frequency and time parameters. Coded excitation is based on the filtering of the transmitted signal using a suitable electric input signal. The aim of the present study was to compare two coded-excitation methods, a chirp- and a wavelet-coded excitation method, to determine the time of flight of the ultrasonic wave, and to investigate the feasibility, the robustness and the precision of the measurement of geometrical and acoustical properties in laboratory conditions. To obtain control experimental data, the two methods were compared with the conventional ultrasonic pulse method. Experiments were conducted on a polyurethane resin sample and two samples of different wood species using two 500 kHz-transducers. The relative errors in the measurement of thickness compared with the results of caliper measurements ranged from 0.13% minimum for the wavelet-coded excitation method to 2.3% maximum for the chirp-coded excitation method. For the relative errors in the measurement of ultrasonic wave velocity, the coded excitation methods showed differences ranging from 0.24% minimum for the wavelet-coded excitation method to 2.62% maximum for the chirp-coded excitation method. Methods based on coded excitation algorithms thus enable accurate measurements of thickness and ultrasonic wave velocity in samples of wood species. Copyright © 2018 Elsevier B.V. All rights reserved.

The Use of Coding Methods to Estimate the Social Behavior Directed toward Peers and Adults of Preschoolers with ASD in TEACCH, LEAP, and Eclectic ''BAU'' Classrooms

ERIC Educational Resources Information Center

Sam, Ann; Reszka, Stephanie; Odom, Samuel; Hume, Kara; Boyd, Brian

2015-01-01

Momentary time sampling, partial-interval recording, and event coding are observational coding methods commonly used to examine the social and challenging behaviors of children at risk for or with developmental delays or disabilities. Yet there is limited research comparing the accuracy of and relationship between these three coding methods. By…

Two high-density recording methods with run-length limited turbo code for holographic data storage system

NASA Astrophysics Data System (ADS)

Nakamura, Yusuke; Hoshizawa, Taku

2016-09-01

Two methods for increasing the data capacity of a holographic data storage system (HDSS) were developed. The first method is called “run-length-limited (RLL) high-density recording”. An RLL modulation has the same effect as enlarging the pixel pitch; namely, it optically reduces the hologram size. Accordingly, the method doubles the raw-data recording density. The second method is called “RLL turbo signal processing”. The RLL turbo code consists of \\text{RLL}(1,∞ ) trellis modulation and an optimized convolutional code. The remarkable point of the developed turbo code is that it employs the RLL modulator and demodulator as parts of the error-correction process. The turbo code improves the capability of error correction more than a conventional LDPC code, even though interpixel interference is generated. These two methods will increase the data density 1.78-fold. Moreover, by simulation and experiment, a data density of 2.4 Tbit/in.2 is confirmed.

The identification of incident cancers in UK primary care databases: a systematic review.

PubMed

Rañopa, Michael; Douglas, Ian; van Staa, Tjeerd; Smeeth, Liam; Klungel, Olaf; Reynolds, Robert; Bhaskaran, Krishnan

2015-01-01

UK primary care databases are frequently used in observational studies with cancer outcomes. We aimed to systematically review methods used by such studies to identify and validate incident cancers of the breast, colorectum, and prostate. Medline and Embase (1980-2013) were searched for UK primary care database studies with incident breast, colorectal, or prostate cancer outcomes. Data on the methods used for case ascertainment were extracted and summarised. Questionnaires were sent to corresponding authors to obtain details about case ascertainment. Eighty-four studies of breast (n = 51), colorectal (n = 54), and prostate cancer (n = 31) were identified; 30 examined >1 cancer type. Among the 84 studies, 57 defined cancers using only diagnosis codes, while 27 required further evidence such as chemotherapy. Few studies described methods used to create cancer code lists (n = 5); or made lists available directly (n = 5). Twenty-eight code lists were received on request from study authors. All included malignant neoplasm diagnosis codes, but there was considerable variation in the specific codes included which was not explained by coding dictionary changes. Code lists also varied in terms of other types of codes included, such as in-situ, cancer morphology, history of cancer, and secondary/suspected/borderline cancer codes. In UK primary care database studies, methods for identifying breast, colorectal, and prostate cancers were often unclear. Code lists were often unavailable, and where provided, we observed variation in the individual codes and types of codes included. Clearer reporting of methods and publication of code lists would improve transparency and reproducibility of studies. Copyright © 2014 John Wiley & Sons, Ltd.

Authorship Attribution of Source Code

ERIC Educational Resources Information Center

Tennyson, Matthew F.

2013-01-01

Authorship attribution of source code is the task of deciding who wrote a program, given its source code. Applications include software forensics, plagiarism detection, and determining software ownership. A number of methods for the authorship attribution of source code have been presented in the past. A review of those existing methods is…

Competitive region orientation code for palmprint verification and identification

NASA Astrophysics Data System (ADS)

Tang, Wenliang

2015-11-01

Orientation features of the palmprint have been widely investigated in coding-based palmprint-recognition methods. Conventional orientation-based coding methods usually used discrete filters to extract the orientation feature of palmprint. However, in real operations, the orientations of the filter usually are not consistent with the lines of the palmprint. We thus propose a competitive region orientation-based coding method. Furthermore, an effective weighted balance scheme is proposed to improve the accuracy of the extracted region orientation. Compared with conventional methods, the region orientation of the palmprint extracted using the proposed method can precisely and robustly describe the orientation feature of the palmprint. Extensive experiments on the baseline PolyU and multispectral palmprint databases are performed and the results show that the proposed method achieves a promising performance in comparison to conventional state-of-the-art orientation-based coding methods in both palmprint verification and identification.

Does my brain want what my eyes like? - How food liking and choice influence spatio-temporal brain dynamics of food viewing.

PubMed

Bielser, Marie-Laure; Crézé, Camille; Murray, Micah M; Toepel, Ulrike

2016-12-01

How food valuation and decision-making influence the perception of food is of major interest to better understand food intake behavior and, by extension, body weight management. Our study investigated behavioral responses and spatio-temporal brain dynamics by means of visual evoked potentials (VEPs) in twenty-two normal-weight participants when viewing pairs of food photographs. Participants rated how much they liked each food item (valuation) and subsequently chose between the two alternative food images. Unsurprisingly, strongly liked foods were also chosen most often. Foods were rated faster as strongly liked than as mildly liked or disliked irrespective of whether they were subsequently chosen over an alternative. Moreover, strongly liked foods were subsequently also chosen faster than the less liked alternatives. Response times during valuation and choice were positively correlated, but only when foods were liked; the faster participants rated foods as strongly liked, the faster they were in choosing the food item over an alternative. VEP modulations by the level of liking attributed as well as the subsequent choice were found as early as 135-180ms after food image onset. Analyses of neural source activity patterns over this time interval revealed an interaction between liking and the subsequent choice within the insula, dorsal frontal and superior parietal regions. The neural responses to food viewing were found to be modulated by the attributed level of liking only when foods were chosen, not when they were dismissed for an alternative. Therein, the responses to disliked foods were generally greater than those to foods that were liked more. Moreover, the responses to disliked but chosen foods were greater than responses to disliked foods which were subsequently dismissed for an alternative offer. Our findings show that the spatio-temporal brain dynamics to food viewing are immediately influenced both by how much foods are liked and by choices taken on them. These valuation and choice processes are subserved by brain regions involved in salience and reward attribution as well as in decision-making processes, which are likely to influence prospective dietary choices in everyday life. Copyright © 2015 Elsevier Inc. All rights reserved.

Understanding Actions of Others: The Electrodynamics of the Left and Right Hemispheres. A High-Density EEG Neuroimaging Study

PubMed Central

Ortigue, Stephanie; Sinigaglia, Corrado; Rizzolatti, Giacomo; Grafton, Scott T.

2010-01-01

Background When we observe an individual performing a motor act (e.g. grasping a cup) we get two types of information on the basis of how the motor act is done and the context: what the agent is doing (i.e. grasping) and the intention underlying it (i.e. grasping for drinking). Here we examined the temporal dynamics of the brain activations that follow the observation of a motor act and underlie the observer's capacity to understand what the agent is doing and why. Methodology/Principal Findings Volunteers were presented with two-frame video-clips. The first frame (T0) showed an object with or without context; the second frame (T1) showed a hand interacting with the object. The volunteers were instructed to understand the intention of the observed actions while their brain activity was recorded with a high-density 128-channel EEG system. Visual event-related potentials (VEPs) were recorded time-locked with the frame showing the hand-object interaction (T1). The data were analyzed by using electrical neuroimaging, which combines a cluster analysis performed on the group-averaged VEPs with the localization of the cortical sources that give rise to different spatio-temporal states of the global electrical field. Electrical neuroimaging results revealed four major steps: 1) bilateral posterior cortical activations; 2) a strong activation of the left posterior temporal and inferior parietal cortices with almost a complete disappearance of activations in the right hemisphere; 3) a significant increase of the activations of the right temporo-parietal region with simultaneously co-active left hemispheric sources, and 4) a significant global decrease of cortical activity accompanied by the appearance of activation of the orbito-frontal cortex. Conclusions/Significance We conclude that the early striking left hemisphere involvement is due to the activation of a lateralized action-observation/action execution network. The activation of this lateralized network mediates the understanding of the goal of object-directed motor acts (mirror mechanism). The successive right hemisphere activation indicates that this hemisphere plays an important role in understanding the intention of others. PMID:20730095

Comparison of electrically evoked cortical potential thresholds generated with subretinal or suprachoroidal placement of a microelectrode array in the rabbit

NASA Astrophysics Data System (ADS)

Yamauchi, Yasuyuki; Franco, Luisa M.; Jackson, Douglas J.; Naber, John F.; Ofer Ziv, R.; Rizzo, Joseph F., III; Kaplan, Henry J.; Enzmann, Volker

2005-03-01

The aim of the study was to directly compare the threshold electrical charge density of the retina (retinal threshold) in rabbits for the generation of electrical evoked potentials (EEP) by delivering electrical stimulation with a custom-made microelectrode array (MEA) implanted into either the subretinal or suprachoroidal space. Nine eyes of seven Dutch-belted rabbits were studied. The electroretinogram (ERG), visual evoked potentials (VEP) and EEP were recorded. Electrodes for the VEP and EEP were placed on the dura mater overlying the visual cortex. The EEP was recorded following electrical stimulation of the MEA placed either subretinally beneath the visual streak of the retina or in the suprachoroidal space in the rabbit eye. An ab externo approach was used for placement of the MEA. Liquid perfluorodecaline (PFCL; 0.4 ml) was placed within the vitreous cavity to flatten the neurosensory retina on the MEA after subretinal implantation. The retinal threshold for generation of an EEP was determined for each MEA placement by three consecutive measurements consisting of 100 computer-averaged recordings. Animals were sacrificed at the conclusion of the experiment and the eyes were enucleated for histological examination. The retinal threshold to generate an EEP was 9 ± 7 nC (0.023 ± 0.016 mC cm-2) within the subretinal space and 150 ± 122 nC (0.375 ± 0.306 mC cm-2) within the suprachoroidal space. Histology showed disruption of the outer retina with subretinal but not suprachoroidal placement. The retinal threshold to elicit an EEP is significantly lower with subretinal placement of the MEA compared to suprachoroidal placement (P < 0.05). The retinal threshold charge density with a subretinal MEA is well below the published charge limit of 1 mC cm-2, which is the level below which chronic stimulation of the retina is considered necessary to avoid tissue damage (Shannon 1992 IEEE Trans. Biomed. Eng. 39 424-6). Supported in part by The Charles D Kelman, MD Postdoctoral Scholar Award 2003 (YY); Boston VA Hospital (V523P-7278); Research to Prevent Blindness, New York City, NY and Kentucky Research Challenge Trust Fund (HJK).

Dynamics of thin-skinned fold and thrust belts with a tilted detachment

NASA Astrophysics Data System (ADS)

Fernandez, Naiara; Kaus, Boris J. P.; Epard, Jean-Luc

2014-05-01

The formation of the Jura fold and thrust belt is linked to the Alpine orogeny. However, it is still a matter of debate why the Jura was formed tens of kilometres far away from the active deformation front while the Molasse basin that lies in between remained mostly undeformed. Progressive thickening of the Molasse basin due to its infill with sediments, and the existence of a tilted potential detachment level at the Triassic evaporitic units, have been pushed forward as the main causes for the detachment of the Molasse basin and the consequent jump of the deformation front from the Alpine front to the position of the Jura at around 22 Ma or later (e.g Willett and Schlunegger, 2010). In order to better understand the dynamics of a thin-skinned fold and thrust belt with a tilted detachment we have performed systematic forward numerical simulations with the 2D thermo-mechanical finite element code MILAMIN_VEP. The modelled setup consists of a tilted detachment, overlain by a sedimentary cover of constant thickness and a wedge shaped basin infill that makes the initial surface slope of the system to be zero. In this study we have tested the importance of the following factors in the dynamics of such a fold and thrust belt evolution: 1) the applied boundary conditions 2) the angle of a uniformly tilted detachment 3) the end displacement of a curved detachment with a flexural foreland basin profile. The implications of the studied factors are discussed for the case of the Jura-Molasse system. Acknowledgements Funding was provided by the European Research Council under the European Community's Seventh Framework program (FP7/2007-2013) ERC Grant agreement #258830. References Willett, S.D. and Schlunegger, F. 2010, The last phase of deposition in the Swiss Molasse Basin: from foredeep to negative-alpha basin. Basin Research 22, 623-639, doi: 10.1111/j.1365-2117.2009.00435.x

Codestream-Based Identification of JPEG 2000 Images with Different Coding Parameters

NASA Astrophysics Data System (ADS)

Watanabe, Osamu; Fukuhara, Takahiro; Kiya, Hitoshi

A method of identifying JPEG 2000 images with different coding parameters, such as code-block sizes, quantization-step sizes, and resolution levels, is presented. It does not produce false-negative matches regardless of different coding parameters (compression rate, code-block size, and discrete wavelet transform (DWT) resolutions levels) or quantization step sizes. This feature is not provided by conventional methods. Moreover, the proposed approach is fast because it uses the number of zero-bit-planes that can be extracted from the JPEG 2000 codestream by only parsing the header information without embedded block coding with optimized truncation (EBCOT) decoding. The experimental results revealed the effectiveness of image identification based on the new method.

Open Rotor Noise Prediction Methods at NASA Langley- A Technology Review

NASA Technical Reports Server (NTRS)

Farassat, F.; Dunn, Mark H.; Tinetti, Ana F.; Nark, Douglas M.

2009-01-01

Open rotors are once again under consideration for propulsion of the future airliners because of their high efficiency. The noise generated by these propulsion systems must meet the stringent noise standards of today to reduce community impact. In this paper we review the open rotor noise prediction methods available at NASA Langley. We discuss three codes called ASSPIN (Advanced Subsonic-Supersonic Propeller Induced Noise), FW - Hpds (Ffowcs Williams-Hawkings with penetrable data surface) and the FSC (Fast Scattering Code). The first two codes are in the time domain and the third code is a frequency domain code. The capabilities of these codes and the input data requirements as well as the output data are presented. Plans for further improvements of these codes are discussed. In particular, a method based on equivalent sources is outlined to get rid of spurious signals in the FW - Hpds code.

An optimization program based on the method of feasible directions: Theory and users guide

NASA Technical Reports Server (NTRS)

Belegundu, Ashok D.; Berke, Laszlo; Patnaik, Surya N.

1994-01-01

The theory and user instructions for an optimization code based on the method of feasible directions are presented. The code was written for wide distribution and ease of attachment to other simulation software. Although the theory of the method of feasible direction was developed in the 1960's, many considerations are involved in its actual implementation as a computer code. Included in the code are a number of features to improve robustness in optimization. The search direction is obtained by solving a quadratic program using an interior method based on Karmarkar's algorithm. The theory is discussed focusing on the important and often overlooked role played by the various parameters guiding the iterations within the program. Also discussed is a robust approach for handling infeasible starting points. The code was validated by solving a variety of structural optimization test problems that have known solutions obtained by other optimization codes. It has been observed that this code is robust: it has solved a variety of problems from different starting points. However, the code is inefficient in that it takes considerable CPU time as compared with certain other available codes. Further work is required to improve its efficiency while retaining its robustness.

Convergence acceleration of the Proteus computer code with multigrid methods

NASA Technical Reports Server (NTRS)

Demuren, A. O.; Ibraheem, S. O.

1992-01-01

Presented here is the first part of a study to implement convergence acceleration techniques based on the multigrid concept in the Proteus computer code. A review is given of previous studies on the implementation of multigrid methods in computer codes for compressible flow analysis. Also presented is a detailed stability analysis of upwind and central-difference based numerical schemes for solving the Euler and Navier-Stokes equations. Results are given of a convergence study of the Proteus code on computational grids of different sizes. The results presented here form the foundation for the implementation of multigrid methods in the Proteus code.

Implementation of radiation shielding calculation methods. Volume 1: Synopsis of methods and summary of results

NASA Technical Reports Server (NTRS)

Capo, M. A.; Disney, R. K.

1971-01-01

The work performed in the following areas is summarized: (1) Analysis of Realistic nuclear-propelled vehicle was analyzed using the Marshall Space Flight Center computer code package. This code package includes one and two dimensional discrete ordinate transport, point kernel, and single scatter techniques, as well as cross section preparation and data processing codes, (2) Techniques were developed to improve the automated data transfer in the coupled computation method of the computer code package and improve the utilization of this code package on the Univac-1108 computer system. (3) The MSFC master data libraries were updated.

Linear chirp phase perturbing approach for finding binary phased codes

NASA Astrophysics Data System (ADS)

Li, Bing C.

2017-05-01

Binary phased codes have many applications in communication and radar systems. These applications require binary phased codes to have low sidelobes in order to reduce interferences and false detection. Barker codes are the ones that satisfy these requirements and they have lowest maximum sidelobes. However, Barker codes have very limited code lengths (equal or less than 13) while many applications including low probability of intercept radar, and spread spectrum communication, require much higher code lengths. The conventional techniques of finding binary phased codes in literatures include exhaust search, neural network, and evolutionary methods, and they all require very expensive computation for large code lengths. Therefore these techniques are limited to find binary phased codes with small code lengths (less than 100). In this paper, by analyzing Barker code, linear chirp, and P3 phases, we propose a new approach to find binary codes. Experiments show that the proposed method is able to find long low sidelobe binary phased codes (code length >500) with reasonable computational cost.

Determination of Problematic ICD-9-CM Subcategories for Further Study of Coding Performance: Delphi Method

PubMed Central

Zeng, Xiaoming; Bell, Paul D

2011-01-01

In this study, we report on a qualitative method known as the Delphi method, used in the first part of a research study for improving the accuracy and reliability of ICD-9-CM coding. A panel of independent coding experts interacted methodically to determine that the three criteria to identify a problematic ICD-9-CM subcategory for further study were cost, volume, and level of coding confusion caused. The Medicare Provider Analysis and Review (MEDPAR) 2007 fiscal year data set as well as suggestions from the experts were used to identify coding subcategories based on cost and volume data. Next, the panelists performed two rounds of independent ranking before identifying Excisional Debridement as the subcategory that causes the most confusion among coders. As a result, they recommended it for further study aimed at improving coding accuracy and variation. This framework can be adopted at different levels for similar studies in need of a schema for determining problematic subcategories of code sets. PMID:21796264

Genome-scale deletion screening of human long non-coding RNAs using a paired-guide RNA CRISPR library

PubMed Central

Zhu, Shiyou; Li, Wei; Liu, Jingze; Chen, Chen-Hao; Liao, Qi; Xu, Ping; Xu, Han; Xiao, Tengfei; Cao, Zhongzheng; Peng, Jingyu; Yuan, Pengfei; Brown, Myles; Liu, Xiaole Shirley; Wei, Wensheng

2017-01-01

CRISPR/Cas9 screens have been widely adopted to analyse coding gene functions, but high throughput screening of non-coding elements using this method is more challenging, because indels caused by a single cut in non-coding regions are unlikely to produce a functional knockout. A high-throughput method to produce deletions of non-coding DNA is needed. Herein, we report a high throughput genomic deletion strategy to screen for functional long non-coding RNAs (lncRNAs) that is based on a lentiviral paired-guide RNA (pgRNA) library. Applying our screening method, we identified 51 lncRNAs that can positively or negatively regulate human cancer cell growth. We individually validated 9 lncRNAs using CRISPR/Cas9-mediated genomic deletion and functional rescue, CRISPR activation or inhibition, and gene expression profiling. Our high-throughput pgRNA genome deletion method should enable rapid identification of functional mammalian non-coding elements. PMID:27798563

A comparison of skyshine computational methods.

PubMed

Hertel, Nolan E; Sweezy, Jeremy E; Shultis, J Kenneth; Warkentin, J Karl; Rose, Zachary J

2005-01-01

A variety of methods employing radiation transport and point-kernel codes have been used to model two skyshine problems. The first problem is a 1 MeV point source of photons on the surface of the earth inside a 2 m tall and 1 m radius silo having black walls. The skyshine radiation downfield from the point source was estimated with and without a 30-cm-thick concrete lid on the silo. The second benchmark problem is to estimate the skyshine radiation downfield from 12 cylindrical canisters emplaced in a low-level radioactive waste trench. The canisters are filled with ion-exchange resin with a representative radionuclide loading, largely 60Co, 134Cs and 137Cs. The solution methods include use of the MCNP code to solve the problem by directly employing variance reduction techniques, the single-scatter point kernel code GGG-GP, the QADMOD-GP point kernel code, the COHORT Monte Carlo code, the NAC International version of the SKYSHINE-III code, the KSU hybrid method and the associated KSU skyshine codes.

Methods of treating complex space vehicle geometry for charged particle radiation transport

NASA Technical Reports Server (NTRS)

Hill, C. W.

1973-01-01

Current methods of treating complex geometry models for space radiation transport calculations are reviewed. The geometric techniques used in three computer codes are outlined. Evaluations of geometric capability and speed are provided for these codes. Although no code development work is included several suggestions for significantly improving complex geometry codes are offered.

The algebraic decoding of the (41, 21, 9) quadratic residue code

NASA Technical Reports Server (NTRS)

Reed, Irving S.; Truong, T. K.; Chen, Xuemin; Yin, Xiaowei

1992-01-01

A new algebraic approach for decoding the quadratic residue (QR) codes, in particular the (41, 21, 9) QR code is presented. The key ideas behind this decoding technique are a systematic application of the Sylvester resultant method to the Newton identities associated with the code syndromes to find the error-locator polynomial, and next a method for determining error locations by solving certain quadratic, cubic and quartic equations over GF(2 exp m) in a new way which uses Zech's logarithms for the arithmetic. The algorithms developed here are suitable for implementation in a programmable microprocessor or special-purpose VLSI chip. It is expected that the algebraic methods developed here can apply generally to other codes such as the BCH and Reed-Solomon codes.

Processing module operating methods, processing modules, and communications systems

DOEpatents

McCown, Steven Harvey; Derr, Kurt W.; Moore, Troy

2014-09-09

A processing module operating method includes using a processing module physically connected to a wireless communications device, requesting that the wireless communications device retrieve encrypted code from a web site and receiving the encrypted code from the wireless communications device. The wireless communications device is unable to decrypt the encrypted code. The method further includes using the processing module, decrypting the encrypted code, executing the decrypted code, and preventing the wireless communications device from accessing the decrypted code. Another processing module operating method includes using a processing module physically connected to a host device, executing an application within the processing module, allowing the application to exchange user interaction data communicated using a user interface of the host device with the host device, and allowing the application to use the host device as a communications device for exchanging information with a remote device distinct from the host device.

A Dual-Channel Acquisition Method Based on Extended Replica Folding Algorithm for Long Pseudo-Noise Code in Inter-Satellite Links.

PubMed

Zhao, Hongbo; Chen, Yuying; Feng, Wenquan; Zhuang, Chen

2018-05-25

Inter-satellite links are an important component of the new generation of satellite navigation systems, characterized by low signal-to-noise ratio (SNR), complex electromagnetic interference and the short time slot of each satellite, which brings difficulties to the acquisition stage. The inter-satellite link in both Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) adopt the long code spread spectrum system. However, long code acquisition is a difficult and time-consuming task due to the long code period. Traditional folding methods such as extended replica folding acquisition search technique (XFAST) and direct average are largely restricted because of code Doppler and additional SNR loss caused by replica folding. The dual folding method (DF-XFAST) and dual-channel method have been proposed to achieve long code acquisition in low SNR and high dynamic situations, respectively, but the former is easily affected by code Doppler and the latter is not fast enough. Considering the environment of inter-satellite links and the problems of existing algorithms, this paper proposes a new long code acquisition algorithm named dual-channel acquisition method based on the extended replica folding algorithm (DC-XFAST). This method employs dual channels for verification. Each channel contains an incoming signal block. Local code samples are folded and zero-padded to the length of the incoming signal block. After a circular FFT operation, the correlation results contain two peaks of the same magnitude and specified relative position. The detection process is eased through finding the two largest values. The verification takes all the full and partial peaks into account. Numerical results reveal that the DC-XFAST method can improve acquisition performance while acquisition speed is guaranteed. The method has a significantly higher acquisition probability than folding methods XFAST and DF-XFAST. Moreover, with the advantage of higher detection probability and lower false alarm probability, it has a lower mean acquisition time than traditional XFAST, DF-XFAST and zero-padding.

CREPT-MCNP code for efficiency calibration of HPGe detectors with the representative point method.

PubMed

Saegusa, Jun

2008-01-01

The representative point method for the efficiency calibration of volume samples has been previously proposed. For smoothly implementing the method, a calculation code named CREPT-MCNP has been developed. The code estimates the position of a representative point which is intrinsic to each shape of volume sample. The self-absorption correction factors are also given to make correction on the efficiencies measured at the representative point with a standard point source. Features of the CREPT-MCNP code are presented.

Investigation of the Use of Erasures in a Concatenated Coding Scheme

NASA Technical Reports Server (NTRS)

Kwatra, S. C.; Marriott, Philip J.

1997-01-01

A new method for declaring erasures in a concatenated coding scheme is investigated. This method is used with the rate 1/2 K = 7 convolutional code and the (255, 223) Reed Solomon code. Errors and erasures Reed Solomon decoding is used. The erasure method proposed uses a soft output Viterbi algorithm and information provided by decoded Reed Solomon codewords in a deinterleaving frame. The results show that a gain of 0.3 dB is possible using a minimum amount of decoding trials.

A motion compensation technique using sliced blocks and its application to hybrid video coding

NASA Astrophysics Data System (ADS)

Kondo, Satoshi; Sasai, Hisao

2005-07-01

This paper proposes a new motion compensation method using "sliced blocks" in DCT-based hybrid video coding. In H.264 ? MPEG-4 Advance Video Coding, a brand-new international video coding standard, motion compensation can be performed by splitting macroblocks into multiple square or rectangular regions. In the proposed method, on the other hand, macroblocks or sub-macroblocks are divided into two regions (sliced blocks) by an arbitrary line segment. The result is that the shapes of the segmented regions are not limited to squares or rectangles, allowing the shapes of the segmented regions to better match the boundaries between moving objects. Thus, the proposed method can improve the performance of the motion compensation. In addition, adaptive prediction of the shape according to the region shape of the surrounding macroblocks can reduce overheads to describe shape information in the bitstream. The proposed method also has the advantage that conventional coding techniques such as mode decision using rate-distortion optimization can be utilized, since coding processes such as frequency transform and quantization are performed on a macroblock basis, similar to the conventional coding methods. The proposed method is implemented in an H.264-based P-picture codec and an improvement in bit rate of 5% is confirmed in comparison with H.264.

High-efficiency Gaussian key reconciliation in continuous variable quantum key distribution

NASA Astrophysics Data System (ADS)

Bai, ZengLiang; Wang, XuYang; Yang, ShenShen; Li, YongMin

2016-01-01

Efficient reconciliation is a crucial step in continuous variable quantum key distribution. The progressive-edge-growth (PEG) algorithm is an efficient method to construct relatively short block length low-density parity-check (LDPC) codes. The qua-sicyclic construction method can extend short block length codes and further eliminate the shortest cycle. In this paper, by combining the PEG algorithm and qua-si-cyclic construction method, we design long block length irregular LDPC codes with high error-correcting capacity. Based on these LDPC codes, we achieve high-efficiency Gaussian key reconciliation with slice recon-ciliation based on multilevel coding/multistage decoding with an efficiency of 93.7%.

Generalized type II hybrid ARQ scheme using punctured convolutional coding

NASA Astrophysics Data System (ADS)

Kallel, Samir; Haccoun, David

1990-11-01

A method is presented to construct rate-compatible convolutional (RCC) codes from known high-rate punctured convolutional codes, obtained from best-rate 1/2 codes. The construction method is rather simple and straightforward, and still yields good codes. Moreover, low-rate codes can be obtained without any limit on the lowest achievable code rate. Based on the RCC codes, a generalized type-II hybrid ARQ scheme, which combines the benefits of the modified type-II hybrid ARQ strategy of Hagenauer (1988) with the code-combining ARQ strategy of Chase (1985), is proposed and analyzed. With the proposed generalized type-II hybrid ARQ strategy, the throughput increases as the starting coding rate increases, and as the channel degrades, it tends to merge with the throughput of rate 1/2 type-II hybrid ARQ schemes with code combining, thus allowing the system to be flexible and adaptive to channel conditions, even under wide noise variations and severe degradations.

High Order Modulation Protograph Codes

NASA Technical Reports Server (NTRS)

Nguyen, Thuy V. (Inventor); Nosratinia, Aria (Inventor); Divsalar, Dariush (Inventor)

2014-01-01

Digital communication coding methods for designing protograph-based bit-interleaved code modulation that is general and applies to any modulation. The general coding framework can support not only multiple rates but also adaptive modulation. The method is a two stage lifting approach. In the first stage, an original protograph is lifted to a slightly larger intermediate protograph. The intermediate protograph is then lifted via a circulant matrix to the expected codeword length to form a protograph-based low-density parity-check code.

RD Optimized, Adaptive, Error-Resilient Transmission of MJPEG2000-Coded Video over Multiple Time-Varying Channels

NASA Astrophysics Data System (ADS)

Bezan, Scott; Shirani, Shahram

2006-12-01

To reliably transmit video over error-prone channels, the data should be both source and channel coded. When multiple channels are available for transmission, the problem extends to that of partitioning the data across these channels. The condition of transmission channels, however, varies with time. Therefore, the error protection added to the data at one instant of time may not be optimal at the next. In this paper, we propose a method for adaptively adding error correction code in a rate-distortion (RD) optimized manner using rate-compatible punctured convolutional codes to an MJPEG2000 constant rate-coded frame of video. We perform an analysis on the rate-distortion tradeoff of each of the coding units (tiles and packets) in each frame and adapt the error correction code assigned to the unit taking into account the bandwidth and error characteristics of the channels. This method is applied to both single and multiple time-varying channel environments. We compare our method with a basic protection method in which data is either not transmitted, transmitted with no protection, or transmitted with a fixed amount of protection. Simulation results show promising performance for our proposed method.

Manual versus automated coding of free-text self-reported medication data in the 45 and Up Study: a validation study.

PubMed

Gnjidic, Danijela; Pearson, Sallie-Anne; Hilmer, Sarah N; Basilakis, Jim; Schaffer, Andrea L; Blyth, Fiona M; Banks, Emily

2015-03-30

Increasingly, automated methods are being used to code free-text medication data, but evidence on the validity of these methods is limited. To examine the accuracy of automated coding of previously keyed in free-text medication data compared with manual coding of original handwritten free-text responses (the 'gold standard'). A random sample of 500 participants (475 with and 25 without medication data in the free-text box) enrolled in the 45 and Up Study was selected. Manual coding involved medication experts keying in free-text responses and coding using Anatomical Therapeutic Chemical (ATC) codes (i.e. chemical substance 7-digit level; chemical subgroup 5-digit; pharmacological subgroup 4-digit; therapeutic subgroup 3-digit). Using keyed-in free-text responses entered by non-experts, the automated approach coded entries using the Australian Medicines Terminology database and assigned corresponding ATC codes. Based on manual coding, 1377 free-text entries were recorded and, of these, 1282 medications were coded to ATCs manually. The sensitivity of automated coding compared with manual coding was 79% (n = 1014) for entries coded at the exact ATC level, and 81.6% (n = 1046), 83.0% (n = 1064) and 83.8% (n = 1074) at the 5, 4 and 3-digit ATC levels, respectively. The sensitivity of automated coding for blank responses was 100% compared with manual coding. Sensitivity of automated coding was highest for prescription medications and lowest for vitamins and supplements, compared with the manual approach. Positive predictive values for automated coding were above 95% for 34 of the 38 individual prescription medications examined. Automated coding for free-text prescription medication data shows very high to excellent sensitivity and positive predictive values, indicating that automated methods can potentially be useful for large-scale, medication-related research.

Identifying complications of interventional procedures from UK routine healthcare databases: a systematic search for methods using clinical codes.

PubMed

Keltie, Kim; Cole, Helen; Arber, Mick; Patrick, Hannah; Powell, John; Campbell, Bruce; Sims, Andrew

2014-11-28

Several authors have developed and applied methods to routine data sets to identify the nature and rate of complications following interventional procedures. But, to date, there has been no systematic search for such methods. The objective of this article was to find, classify and appraise published methods, based on analysis of clinical codes, which used routine healthcare databases in a United Kingdom setting to identify complications resulting from interventional procedures. A literature search strategy was developed to identify published studies that referred, in the title or abstract, to the name or acronym of a known routine healthcare database and to complications from procedures or devices. The following data sources were searched in February and March 2013: Cochrane Methods Register, Conference Proceedings Citation Index - Science, Econlit, EMBASE, Health Management Information Consortium, Health Technology Assessment database, MathSciNet, MEDLINE, MEDLINE in-process, OAIster, OpenGrey, Science Citation Index Expanded and ScienceDirect. Of the eligible papers, those which reported methods using clinical coding were classified and summarised in tabular form using the following headings: routine healthcare database; medical speciality; method for identifying complications; length of follow-up; method of recording comorbidity. The benefits and limitations of each approach were assessed. From 3688 papers identified from the literature search, 44 reported the use of clinical codes to identify complications, from which four distinct methods were identified: 1) searching the index admission for specified clinical codes, 2) searching a sequence of admissions for specified clinical codes, 3) searching for specified clinical codes for complications from procedures and devices within the International Classification of Diseases 10th revision (ICD-10) coding scheme which is the methodology recommended by NHS Classification Service, and 4) conducting manual clinical review of diagnostic and procedure codes. The four distinct methods identifying complication from codified data offer great potential in generating new evidence on the quality and safety of new procedures using routine data. However the most robust method, using the methodology recommended by the NHS Classification Service, was the least frequently used, highlighting that much valuable observational data is being ignored.

Team interaction during surgery: a systematic review of communication coding schemes.

PubMed

Tiferes, Judith; Bisantz, Ann M; Guru, Khurshid A

2015-05-15

Communication problems have been systematically linked to human errors in surgery and a deep understanding of the underlying processes is essential. Although a number of tools exist to assess nontechnical skills, methods to study communication and other team-related processes are far from being standardized, making comparisons challenging. We conducted a systematic review to analyze methods used to study events in the operating room (OR) and to develop a synthesized coding scheme for OR team communication. Six electronic databases were accessed to search for articles that collected individual events during surgery and included detailed coding schemes. Additional articles were added based on cross-referencing. That collection was then classified based on type of events collected, environment type (real or simulated), number of procedures, type of surgical task, team characteristics, method of data collection, and coding scheme characteristics. All dimensions within each coding scheme were grouped based on emergent content similarity. Categories drawn from articles, which focused on communication events, were further analyzed and synthesized into one common coding scheme. A total of 34 of 949 articles met the inclusion criteria. The methodological characteristics and coding dimensions of the articles were summarized. A priori coding was used in nine studies. The synthesized coding scheme for OR communication included six dimensions as follows: information flow, period, statement type, topic, communication breakdown, and effects of communication breakdown. The coding scheme provides a standardized coding method for OR communication, which can be used to develop a priori codes for future studies especially in comparative effectiveness research. Copyright © 2015 Elsevier Inc. All rights reserved.

Simulation of spacecraft attitude dynamics using TREETOPS and model-specific computer Codes

NASA Technical Reports Server (NTRS)

Cochran, John E.; No, T. S.; Fitz-Coy, Norman G.

1989-01-01

The simulation of spacecraft attitude dynamics and control using the generic, multi-body code called TREETOPS and other codes written especially to simulate particular systems is discussed. Differences in the methods used to derive equations of motion--Kane's method for TREETOPS and the Lagrangian and Newton-Euler methods, respectively, for the other two codes--are considered. Simulation results from the TREETOPS code are compared with those from the other two codes for two example systems. One system is a chain of rigid bodies; the other consists of two rigid bodies attached to a flexible base body. Since the computer codes were developed independently, consistent results serve as a verification of the correctness of all the programs. Differences in the results are discussed. Results for the two-rigid-body, one-flexible-body system are useful also as information on multi-body, flexible, pointing payload dynamics.

Digital barcodes of suspension array using laser induced breakdown spectroscopy

PubMed Central

He, Qinghua; Liu, Yixi; He, Yonghong; Zhu, Liang; Zhang, Yilong; Shen, Zhiyuan

2016-01-01

We show a coding method of suspension array based on the laser induced breakdown spectroscopy (LIBS), which promotes the barcodes from analog to digital. As the foundation of digital optical barcodes, nanocrystals encoded microspheres are prepared with self-assembly encapsulation method. We confirm that digital multiplexing of LIBS-based coding method becomes feasible since the microsphere can be coded with direct read-out data of wavelengths, and the method can avoid fluorescence signal crosstalk between barcodes and analyte tags, which lead to overall advantages in accuracy and stability to current fluorescent multicolor coding method. This demonstration increases the capability of multiplexed detection and accurate filtrating, expanding more extensive applications of suspension array in life science. PMID:27808270

Probability Quantization for Multiplication-Free Binary Arithmetic Coding

NASA Technical Reports Server (NTRS)

Cheung, K. -M.

1995-01-01

A method has been developed to improve on Witten's binary arithmetic coding procedure of tracking a high value and a low value. The new method approximates the probability of the less probable symbol, which improves the worst-case coding efficiency.

Multimodal Discriminative Binary Embedding for Large-Scale Cross-Modal Retrieval.

PubMed

Wang, Di; Gao, Xinbo; Wang, Xiumei; He, Lihuo; Yuan, Bo

2016-10-01

Multimodal hashing, which conducts effective and efficient nearest neighbor search across heterogeneous data on large-scale multimedia databases, has been attracting increasing interest, given the explosive growth of multimedia content on the Internet. Recent multimodal hashing research mainly aims at learning the compact binary codes to preserve semantic information given by labels. The overwhelming majority of these methods are similarity preserving approaches which approximate pairwise similarity matrix with Hamming distances between the to-be-learnt binary hash codes. However, these methods ignore the discriminative property in hash learning process, which results in hash codes from different classes undistinguished, and therefore reduces the accuracy and robustness for the nearest neighbor search. To this end, we present a novel multimodal hashing method, named multimodal discriminative binary embedding (MDBE), which focuses on learning discriminative hash codes. First, the proposed method formulates the hash function learning in terms of classification, where the binary codes generated by the learned hash functions are expected to be discriminative. And then, it exploits the label information to discover the shared structures inside heterogeneous data. Finally, the learned structures are preserved for hash codes to produce similar binary codes in the same class. Hence, the proposed MDBE can preserve both discriminability and similarity for hash codes, and will enhance retrieval accuracy. Thorough experiments on benchmark data sets demonstrate that the proposed method achieves excellent accuracy and competitive computational efficiency compared with the state-of-the-art methods for large-scale cross-modal retrieval task.

Concurrent error detecting codes for arithmetic processors

NASA Technical Reports Server (NTRS)

Lim, R. S.

1979-01-01

A method of concurrent error detection for arithmetic processors is described. Low-cost residue codes with check-length l and checkbase m = 2 to the l power - 1 are described for checking arithmetic operations of addition, subtraction, multiplication, division complement, shift, and rotate. Of the three number representations, the signed-magnitude representation is preferred for residue checking. Two methods of residue generation are described: the standard method of using modulo m adders and the method of using a self-testing residue tree. A simple single-bit parity-check code is described for checking the logical operations of XOR, OR, and AND, and also the arithmetic operations of complement, shift, and rotate. For checking complement, shift, and rotate, the single-bit parity-check code is simpler to implement than the residue codes.

Performance Bounds on Two Concatenated, Interleaved Codes

NASA Technical Reports Server (NTRS)

Moision, Bruce; Dolinar, Samuel

2010-01-01

A method has been developed of computing bounds on the performance of a code comprised of two linear binary codes generated by two encoders serially concatenated through an interleaver. Originally intended for use in evaluating the performances of some codes proposed for deep-space communication links, the method can also be used in evaluating the performances of short-block-length codes in other applications. The method applies, more specifically, to a communication system in which following processes take place: At the transmitter, the original binary information that one seeks to transmit is first processed by an encoder into an outer code (Co) characterized by, among other things, a pair of numbers (n,k), where n (n > k)is the total number of code bits associated with k information bits and n k bits are used for correcting or at least detecting errors. Next, the outer code is processed through either a block or a convolutional interleaver. In the block interleaver, the words of the outer code are processed in blocks of I words. In the convolutional interleaver, the interleaving operation is performed bit-wise in N rows with delays that are multiples of B bits. The output of the interleaver is processed through a second encoder to obtain an inner code (Ci) characterized by (ni,ki). The output of the inner code is transmitted over an additive-white-Gaussian- noise channel characterized by a symbol signal-to-noise ratio (SNR) Es/No and a bit SNR Eb/No. At the receiver, an inner decoder generates estimates of bits. Depending on whether a block or a convolutional interleaver is used at the transmitter, the sequence of estimated bits is processed through a block or a convolutional de-interleaver, respectively, to obtain estimates of code words. Then the estimates of the code words are processed through an outer decoder, which generates estimates of the original information along with flags indicating which estimates are presumed to be correct and which are found to be erroneous. From the perspective of the present method, the topic of major interest is the performance of the communication system as quantified in the word-error rate and the undetected-error rate as functions of the SNRs and the total latency of the interleaver and inner code. The method is embodied in equations that describe bounds on these functions. Throughout the derivation of the equations that embody the method, it is assumed that the decoder for the outer code corrects any error pattern of t or fewer errors, detects any error pattern of s or fewer errors, may detect some error patterns of more than s errors, and does not correct any patterns of more than t errors. Because a mathematically complete description of the equations that embody the method and of the derivation of the equations would greatly exceed the space available for this article, it must suffice to summarize by reporting that the derivation includes consideration of several complex issues, including relationships between latency and memory requirements for block and convolutional codes, burst error statistics, enumeration of error-event intersections, and effects of different interleaving depths. In a demonstration, the method was used to calculate bounds on the performances of several communication systems, each based on serial concatenation of a (63,56) expurgated Hamming code with a convolutional inner code through a convolutional interleaver. The bounds calculated by use of the method were compared with results of numerical simulations of performances of the systems to show the regions where the bounds are tight (see figure).

Development of a new lattice physics code robin for PWR application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, S.; Chen, G.

2013-07-01

This paper presents a description of methodologies and preliminary verification results of a new lattice physics code ROBIN, being developed for PWR application at Shanghai NuStar Nuclear Power Technology Co., Ltd. The methods used in ROBIN to fulfill various tasks of lattice physics analysis are an integration of historical methods and new methods that came into being very recently. Not only these methods like equivalence theory for resonance treatment and method of characteristics for neutron transport calculation are adopted, as they are applied in many of today's production-level LWR lattice codes, but also very useful new methods like the enhancedmore » neutron current method for Dancoff correction in large and complicated geometry and the log linear rate constant power depletion method for Gd-bearing fuel are implemented in the code. A small sample of verification results are provided to illustrate the type of accuracy achievable using ROBIN. It is demonstrated that ROBIN is capable of satisfying most of the needs for PWR lattice analysis and has the potential to become a production quality code in the future. (authors)« less

Method for calculating internal radiation and ventilation with the ADINAT heat-flow code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butkovich, T.R.; Montan, D.N.

1980-04-01

One objective of the spent fuel test in Climax Stock granite (SFTC) is to correctly model the thermal transport, and the changes in the stress field and accompanying displacements from the application of the thermal loads. We have chosen the ADINA and ADINAT finite element codes to do these calculations. ADINAT is a heat transfer code compatible to the ADINA displacement and stress analysis code. The heat flow problem encountered at SFTC requires a code with conduction, radiation, and ventilation capabilities, which the present version of ADINAT does not have. We have devised a method for calculating internal radiation andmore » ventilation with the ADINAT code. This method effectively reproduces the results from the TRUMP multi-dimensional finite difference code, which correctly models radiative heat transport between drift surfaces, conductive and convective thermal transport to and through air in the drifts, and mass flow of air in the drifts. The temperature histories for each node in the finite element mesh calculated with ADINAT using this method can be used directly in the ADINA thermal-mechanical calculation.« less

25 CFR 900.125 - What shall a construction contract proposal contain?

Code of Federal Regulations, 2012 CFR

2012-04-01

... tribal building codes and engineering standards; (4) Structural integrity; (5) Accountability of funds..., standards and methods (including national, regional, state, or tribal building codes or construction... methods (including national, regional, state, or tribal building codes or construction industry standards...

25 CFR 900.125 - What shall a construction contract proposal contain?

Code of Federal Regulations, 2014 CFR

2014-04-01

... tribal building codes and engineering standards; (4) Structural integrity; (5) Accountability of funds..., standards and methods (including national, regional, state, or tribal building codes or construction... methods (including national, regional, state, or tribal building codes or construction industry standards...

25 CFR 900.125 - What shall a construction contract proposal contain?

Code of Federal Regulations, 2013 CFR

2013-04-01

... tribal building codes and engineering standards; (4) Structural integrity; (5) Accountability of funds..., standards and methods (including national, regional, state, or tribal building codes or construction... methods (including national, regional, state, or tribal building codes or construction industry standards...

25 CFR 900.125 - What shall a construction contract proposal contain?

Code of Federal Regulations, 2011 CFR

2011-04-01

... tribal building codes and engineering standards; (4) Structural integrity; (5) Accountability of funds..., standards and methods (including national, regional, state, or tribal building codes or construction... methods (including national, regional, state, or tribal building codes or construction industry standards...

25 CFR 900.125 - What shall a construction contract proposal contain?

Code of Federal Regulations, 2010 CFR

2010-04-01

... tribal building codes and engineering standards; (4) Structural integrity; (5) Accountability of funds..., standards and methods (including national, regional, state, or tribal building codes or construction... methods (including national, regional, state, or tribal building codes or construction industry standards...

TORT/MCNP coupling method for the calculation of neutron flux around a core of BWR.

PubMed

Kurosawa, Masahiko

2005-01-01

For the analysis of BWR neutronics performance, accurate data are required for neutron flux distribution over the In-Reactor Pressure Vessel equipments taking into account the detailed geometrical arrangement. The TORT code can calculate neutron flux around a core of BWR in a three-dimensional geometry model, but has difficulties in fine geometrical modelling and lacks huge computer resource. On the other hand, the MCNP code enables the calculation of the neutron flux with a detailed geometry model, but requires very long sampling time to give enough number of particles. Therefore, a TORT/MCNP coupling method has been developed to eliminate the two problems mentioned above in each code. In this method, the TORT code calculates angular flux distribution on the core surface and the MCNP code calculates neutron spectrum at the points of interest using the flux distribution. The coupling method will be used as the DOT-DOMINO-MORSE code system. This TORT/MCNP coupling method was applied to calculate the neutron flux at points where induced radioactivity data were measured for 54Mn and 60Co and the radioactivity calculations based on the neutron flux obtained from the above method were compared with the measured data.

Zebra: An advanced PWR lattice code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, L.; Wu, H.; Zheng, Y.

2012-07-01

This paper presents an overview of an advanced PWR lattice code ZEBRA developed at NECP laboratory in Xi'an Jiaotong Univ.. The multi-group cross-section library is generated from the ENDF/B-VII library by NJOY and the 361-group SHEM structure is employed. The resonance calculation module is developed based on sub-group method. The transport solver is Auto-MOC code, which is a self-developed code based on the Method of Characteristic and the customization of AutoCAD software. The whole code is well organized in a modular software structure. Some numerical results during the validation of the code demonstrate that this code has a good precisionmore » and a high efficiency. (authors)« less

Spatio-Temporal Brain Mapping of Motion-Onset VEPs Combined with fMRI and Retinotopic Maps

PubMed Central

Pitzalis, Sabrina; Strappini, Francesca; De Gasperis, Marco; Bultrini, Alessandro; Di Russo, Francesco

2012-01-01

Neuroimaging studies have identified several motion-sensitive visual areas in the human brain, but the time course of their activation cannot be measured with these techniques. In the present study, we combined electrophysiological and neuroimaging methods (including retinotopic brain mapping) to determine the spatio-temporal profile of motion-onset visual evoked potentials for slow and fast motion stimuli and to localize its neural generators. We found that cortical activity initiates in the primary visual area (V1) for slow stimuli, peaking 100 ms after the onset of motion. Subsequently, activity in the mid-temporal motion-sensitive areas, MT+, peaked at 120 ms, followed by peaks in activity in the more dorsal area, V3A, at 160 ms and the lateral occipital complex at 180 ms. Approximately 250 ms after stimulus onset, activity fast motion stimuli was predominant in area V6 along the parieto-occipital sulcus. Finally, at 350 ms (100 ms after the motion offset) brain activity was visible again in area V1. For fast motion stimuli, the spatio-temporal brain pattern was similar, except that the first activity was detected at 70 ms in area MT+. Comparing functional magnetic resonance data for slow vs. fast motion, we found signs of slow-fast motion stimulus topography along the posterior brain in at least three cortical regions (MT+, V3A and LOR). PMID:22558222

Transcoding method from H.264/AVC to high efficiency video coding based on similarity of intraprediction, interprediction, and motion vector

NASA Astrophysics Data System (ADS)

Liu, Mei-Feng; Zhong, Guo-Yun; He, Xiao-Hai; Qing, Lin-Bo

2016-09-01

Currently, most video resources on line are encoded in the H.264/AVC format. More fluent video transmission can be obtained if these resources are encoded in the newest international video coding standard: high efficiency video coding (HEVC). In order to improve the video transmission and storage on line, a transcoding method from H.264/AVC to HEVC is proposed. In this transcoding algorithm, the coding information of intraprediction, interprediction, and motion vector (MV) in H.264/AVC video stream are used to accelerate the coding in HEVC. It is found through experiments that the region of interprediction in HEVC overlaps that in H.264/AVC. Therefore, the intraprediction for the region in HEVC, which is interpredicted in H.264/AVC, can be skipped to reduce coding complexity. Several macroblocks in H.264/AVC are combined into one PU in HEVC when the MV difference between two of the macroblocks in H.264/AVC is lower than a threshold. This method selects only one coding unit depth and one prediction unit (PU) mode to reduce the coding complexity. An MV interpolation method of combined PU in HEVC is proposed according to the areas and distances between the center of one macroblock in H.264/AVC and that of the PU in HEVC. The predicted MV accelerates the motion estimation for HEVC coding. The simulation results show that our proposed algorithm achieves significant coding time reduction with a little loss in bitrates distortion rate, compared to the existing transcoding algorithms and normal HEVC coding.

Development and evaluation of a Naïve Bayesian model for coding causation of workers’ compensation claims☆

PubMed Central

Bertke, S. J.; Meyers, A. R.; Wurzelbacher, S. J.; Bell, J.; Lampl, M. L.; Robins, D.

2015-01-01

Introduction Tracking and trending rates of injuries and illnesses classified as musculoskeletal disorders caused by ergonomic risk factors such as overexertion and repetitive motion (MSDs) and slips, trips, or falls (STFs) in different industry sectors is of high interest to many researchers. Unfortunately, identifying the cause of injuries and illnesses in large datasets such as workers’ compensation systems often requires reading and coding the free form accident text narrative for potentially millions of records. Method To alleviate the need for manual coding, this paper describes and evaluates a computer auto-coding algorithm that demonstrated the ability to code millions of claims quickly and accurately by learning from a set of previously manually coded claims. Conclusions The auto-coding program was able to code claims as a musculoskeletal disorders, STF or other with approximately 90% accuracy. Impact on industry The program developed and discussed in this paper provides an accurate and efficient method for identifying the causation of workers’ compensation claims as a STF or MSD in a large database based on the unstructured text narrative and resulting injury diagnoses. The program coded thousands of claims in minutes. The method described in this paper can be used by researchers and practitioners to relieve the manual burden of reading and identifying the causation of claims as a STF or MSD. Furthermore, the method can be easily generalized to code/classify other unstructured text narratives. PMID:23206504

Content Coding of Psychotherapy Transcripts Using Labeled Topic Models.

PubMed

Gaut, Garren; Steyvers, Mark; Imel, Zac E; Atkins, David C; Smyth, Padhraic

2017-03-01

Psychotherapy represents a broad class of medical interventions received by millions of patients each year. Unlike most medical treatments, its primary mechanisms are linguistic; i.e., the treatment relies directly on a conversation between a patient and provider. However, the evaluation of patient-provider conversation suffers from critical shortcomings, including intensive labor requirements, coder error, nonstandardized coding systems, and inability to scale up to larger data sets. To overcome these shortcomings, psychotherapy analysis needs a reliable and scalable method for summarizing the content of treatment encounters. We used a publicly available psychotherapy corpus from Alexander Street press comprising a large collection of transcripts of patient-provider conversations to compare coding performance for two machine learning methods. We used the labeled latent Dirichlet allocation (L-LDA) model to learn associations between text and codes, to predict codes in psychotherapy sessions, and to localize specific passages of within-session text representative of a session code. We compared the L-LDA model to a baseline lasso regression model using predictive accuracy and model generalizability (measured by calculating the area under the curve (AUC) from the receiver operating characteristic curve). The L-LDA model outperforms the lasso logistic regression model at predicting session-level codes with average AUC scores of 0.79, and 0.70, respectively. For fine-grained level coding, L-LDA and logistic regression are able to identify specific talk-turns representative of symptom codes. However, model performance for talk-turn identification is not yet as reliable as human coders. We conclude that the L-LDA model has the potential to be an objective, scalable method for accurate automated coding of psychotherapy sessions that perform better than comparable discriminative methods at session-level coding and can also predict fine-grained codes.

Content Coding of Psychotherapy Transcripts Using Labeled Topic Models

PubMed Central

Gaut, Garren; Steyvers, Mark; Imel, Zac E; Atkins, David C; Smyth, Padhraic

2016-01-01

Psychotherapy represents a broad class of medical interventions received by millions of patients each year. Unlike most medical treatments, its primary mechanisms are linguistic; i.e., the treatment relies directly on a conversation between a patient and provider. However, the evaluation of patient-provider conversation suffers from critical shortcomings, including intensive labor requirements, coder error, non-standardized coding systems, and inability to scale up to larger data sets. To overcome these shortcomings, psychotherapy analysis needs a reliable and scalable method for summarizing the content of treatment encounters. We used a publicly-available psychotherapy corpus from Alexander Street press comprising a large collection of transcripts of patient-provider conversations to compare coding performance for two machine learning methods. We used the Labeled Latent Dirichlet Allocation (L-LDA) model to learn associations between text and codes, to predict codes in psychotherapy sessions, and to localize specific passages of within-session text representative of a session code. We compared the L-LDA model to a baseline lasso regression model using predictive accuracy and model generalizability (measured by calculating the area under the curve (AUC) from the receiver operating characteristic (ROC) curve). The L-LDA model outperforms the lasso logistic regression model at predicting session-level codes with average AUC scores of .79, and .70, respectively. For fine-grained level coding, L-LDA and logistic regression are able to identify specific talk-turns representative of symptom codes. However, model performance for talk-turn identification is not yet as reliable as human coders. We conclude that the L-LDA model has the potential to be an objective, scaleable method for accurate automated coding of psychotherapy sessions that performs better than comparable discriminative methods at session-level coding and can also predict fine-grained codes. PMID:26625437

Computing travel time when the exact address is unknown: a comparison of point and polygon ZIP code approximation methods.

PubMed

Berke, Ethan M; Shi, Xun

2009-04-29

Travel time is an important metric of geographic access to health care. We compared strategies of estimating travel times when only subject ZIP code data were available. Using simulated data from New Hampshire and Arizona, we estimated travel times to nearest cancer centers by using: 1) geometric centroid of ZIP code polygons as origins, 2) population centroids as origin, 3) service area rings around each cancer center, assigning subjects to rings by assuming they are evenly distributed within their ZIP code, 4) service area rings around each center, assuming the subjects follow the population distribution within the ZIP code. We used travel times based on street addresses as true values to validate estimates. Population-based methods have smaller errors than geometry-based methods. Within categories (geometry or population), centroid and service area methods have similar errors. Errors are smaller in urban areas than in rural areas. Population-based methods are superior to the geometry-based methods, with the population centroid method appearing to be the best choice for estimating travel time. Estimates in rural areas are less reliable.

A research coding method for the basic patient-centered interview.

PubMed

Grayson-Sneed, Katelyn A; Smith, Sandi W; Smith, Robert C

2017-03-01

To develop a more reliable coding method of medical interviewing focused on data-gathering and emotion-handling. Two trained (30h) undergraduates rated videotaped interviews from 127 resident-simulated patient (SP) interactions. Trained on 45 videotapes, raters coded 25 of 127 study set tapes for patient-centeredness. Guetzkow's U, Cohen's Kappa, and percent of agreement were used to measure raters' reliability in unitizing and coding residents' skills for eliciting: agenda (3 yes/no items), physical story (2), personal story (6), emotional story (15), using indirect skills (4), and general patient-centeredness (3). 45 items were dichotomized from the earlier, Likert scale-based method and were reduced to 33 during training. Guetzkow's U ranged from 0.00 to 0.087. Kappa ranged from 0.86 to 1.00 for the 6 variables and 33 individual items. The overall kappa was 0.90, and percent of agreement was 97.5%. Percent of agreement by item ranged from 84 to 100%. A simple, highly reliable coding method, weighted (by no. of items) to highlight personal elements of an interview, was developed and is recommended as a criterion standard research coding method. An easily conducted, reliable coding procedure can be the basis for everyday questionnaires like patient satisfaction with patient-centeredness. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Conducting Retrospective Ontological Clinical Trials in ICD-9-CM in the Age of ICD-10-CM.

PubMed

Venepalli, Neeta K; Shergill, Ardaman; Dorestani, Parvaneh; Boyd, Andrew D

2014-01-01

To quantify the impact of International Classification of Disease 10th Revision Clinical Modification (ICD-10-CM) transition in cancer clinical trials by comparing coding accuracy and data discontinuity in backward ICD-10-CM to ICD-9-CM mapping via two tools, and to develop a standard ICD-9-CM and ICD-10-CM bridging methodology for retrospective analyses. While the transition to ICD-10-CM has been delayed until October 2015, its impact on cancer-related studies utilizing ICD-9-CM diagnoses has been inadequately explored. Three high impact journals with broad national and international readerships were reviewed for cancer-related studies utilizing ICD-9-CM diagnoses codes in study design, methods, or results. Forward ICD-9-CM to ICD-10-CM mapping was performing using a translational methodology with the Motif web portal ICD-9-CM conversion tool. Backward mapping from ICD-10-CM to ICD-9-CM was performed using both Centers for Medicare and Medicaid Services (CMS) general equivalence mappings (GEMs) files and the Motif web portal tool. Generated ICD-9-CM codes were compared with the original ICD-9-CM codes to assess data accuracy and discontinuity. While both methods yielded additional ICD-9-CM codes, the CMS GEMs method provided incomplete coverage with 16 of the original ICD-9-CM codes missing, whereas the Motif web portal method provided complete coverage. Of these 16 codes, 12 ICD-9-CM codes were present in 2010 Illinois Medicaid data, and accounted for 0.52% of patient encounters and 0.35% of total Medicaid reimbursements. Extraneous ICD-9-CM codes from both methods (Centers for Medicare and Medicaid Services general equivalent mapping [CMS GEMs, n = 161; Motif web portal, n = 246]) in excess of original ICD-9-CM codes accounted for 2.1% and 2.3% of total patient encounters and 3.4% and 4.1% of total Medicaid reimbursements from the 2010 Illinois Medicare database. Longitudinal data analyses post-ICD-10-CM transition will require backward ICD-10-CM to ICD-9-CM coding, and data comparison for accuracy. Researchers must be aware that all methods for backward coding are not comparable in yielding original ICD-9-CM codes. The mandated delay is an opportunity for organizations to better understand areas of financial risk with regards to data management via backward coding. Our methodology is relevant for all healthcare-related coding data, and can be replicated by organizations as a strategy to mitigate financial risk.

Construction method of QC-LDPC codes based on multiplicative group of finite field in optical communication

NASA Astrophysics Data System (ADS)

Huang, Sheng; Ao, Xiang; Li, Yuan-yuan; Zhang, Rui

2016-09-01

In order to meet the needs of high-speed development of optical communication system, a construction method of quasi-cyclic low-density parity-check (QC-LDPC) codes based on multiplicative group of finite field is proposed. The Tanner graph of parity check matrix of the code constructed by this method has no cycle of length 4, and it can make sure that the obtained code can get a good distance property. Simulation results show that when the bit error rate ( BER) is 10-6, in the same simulation environment, the net coding gain ( NCG) of the proposed QC-LDPC(3 780, 3 540) code with the code rate of 93.7% in this paper is improved by 2.18 dB and 1.6 dB respectively compared with those of the RS(255, 239) code in ITU-T G.975 and the LDPC(3 2640, 3 0592) code in ITU-T G.975.1. In addition, the NCG of the proposed QC-LDPC(3 780, 3 540) code is respectively 0.2 dB and 0.4 dB higher compared with those of the SG-QC-LDPC(3 780, 3 540) code based on the two different subgroups in finite field and the AS-QC-LDPC(3 780, 3 540) code based on the two arbitrary sets of a finite field. Thus, the proposed QC-LDPC(3 780, 3 540) code in this paper can be well applied in optical communication systems.

Molecular cancer classification using a meta-sample-based regularized robust coding method.

PubMed

Wang, Shu-Lin; Sun, Liuchao; Fang, Jianwen

2014-01-01

Previous studies have demonstrated that machine learning based molecular cancer classification using gene expression profiling (GEP) data is promising for the clinic diagnosis and treatment of cancer. Novel classification methods with high efficiency and prediction accuracy are still needed to deal with high dimensionality and small sample size of typical GEP data. Recently the sparse representation (SR) method has been successfully applied to the cancer classification. Nevertheless, its efficiency needs to be improved when analyzing large-scale GEP data. In this paper we present the meta-sample-based regularized robust coding classification (MRRCC), a novel effective cancer classification technique that combines the idea of meta-sample-based cluster method with regularized robust coding (RRC) method. It assumes that the coding residual and the coding coefficient are respectively independent and identically distributed. Similar to meta-sample-based SR classification (MSRC), MRRCC extracts a set of meta-samples from the training samples, and then encodes a testing sample as the sparse linear combination of these meta-samples. The representation fidelity is measured by the l2-norm or l1-norm of the coding residual. Extensive experiments on publicly available GEP datasets demonstrate that the proposed method is more efficient while its prediction accuracy is equivalent to existing MSRC-based methods and better than other state-of-the-art dimension reduction based methods.

Performance of automated and manual coding systems for occupational data: a case study of historical records.

PubMed

Patel, Mehul D; Rose, Kathryn M; Owens, Cindy R; Bang, Heejung; Kaufman, Jay S

2012-03-01

Occupational data are a common source of workplace exposure and socioeconomic information in epidemiologic research. We compared the performance of two occupation coding methods, an automated software and a manual coder, using occupation and industry titles from U.S. historical records. We collected parental occupational data from 1920-40s birth certificates, Census records, and city directories on 3,135 deceased individuals in the Atherosclerosis Risk in Communities (ARIC) study. Unique occupation-industry narratives were assigned codes by a manual coder and the Standardized Occupation and Industry Coding software program. We calculated agreement between coding methods of classification into major Census occupational groups. Automated coding software assigned codes to 71% of occupations and 76% of industries. Of this subset coded by software, 73% of occupation codes and 69% of industry codes matched between automated and manual coding. For major occupational groups, agreement improved to 89% (kappa = 0.86). Automated occupational coding is a cost-efficient alternative to manual coding. However, some manual coding is required to code incomplete information. We found substantial variability between coders in the assignment of occupations although not as large for major groups.

Decision Process to Identify Lessons for Transition to a Distributed (or Blended) Learning Instructional Format

DTIC Science & Technology

2009-09-01

instructional format. Using a mixed- method coding and analysis approach, the sample of POIs were categorized, coded, statistically analyzed, and a... Method SECURITY CLASSIFICATION OF 19. LIMITATION OF 20. NUMBER 21. RESPONSIBLE PERSON 16. REPORT Unclassified 17. ABSTRACT...transition to a distributed (or blended) learning format. Procedure: A mixed- methods approach, combining qualitative coding procedures with basic

Method of Error Floor Mitigation in Low-Density Parity-Check Codes

NASA Technical Reports Server (NTRS)

Hamkins, Jon (Inventor)

2014-01-01

A digital communication decoding method for low-density parity-check coded messages. The decoding method decodes the low-density parity-check coded messages within a bipartite graph having check nodes and variable nodes. Messages from check nodes are partially hard limited, so that every message which would otherwise have a magnitude at or above a certain level is re-assigned to a maximum magnitude.

Mal-Xtract: Hidden Code Extraction using Memory Analysis

NASA Astrophysics Data System (ADS)

Lim, Charles; Syailendra Kotualubun, Yohanes; Suryadi; Ramli, Kalamullah

2017-01-01

Software packer has been used effectively to hide the original code inside a binary executable, making it more difficult for existing signature based anti malware software to detect malicious code inside the executable. A new method of written and rewritten memory section is introduced to to detect the exact end time of unpacking routine and extract original code from packed binary executable using Memory Analysis running in an software emulated environment. Our experiment results show that at least 97% of the original code from the various binary executable packed with different software packers could be extracted. The proposed method has also been successfully extracted hidden code from recent malware family samples.

Rate-Compatible Protograph LDPC Codes

NASA Technical Reports Server (NTRS)

Nguyen, Thuy V. (Inventor); Nosratinia, Aria (Inventor); Divsalar, Dariush (Inventor)

2014-01-01

Digital communication coding methods resulting in rate-compatible low density parity-check (LDPC) codes built from protographs. Described digital coding methods start with a desired code rate and a selection of the numbers of variable nodes and check nodes to be used in the protograph. Constraints are set to satisfy a linear minimum distance growth property for the protograph. All possible edges in the graph are searched for the minimum iterative decoding threshold and the protograph with the lowest iterative decoding threshold is selected. Protographs designed in this manner are used in decode and forward relay channels.

Fast H.264/AVC FRExt intra coding using belief propagation.

PubMed

Milani, Simone

2011-01-01

In the H.264/AVC FRExt coder, the coding performance of Intra coding significantly overcomes the previous still image coding standards, like JPEG2000, thanks to a massive use of spatial prediction. Unfortunately, the adoption of an extensive set of predictors induces a significant increase of the computational complexity required by the rate-distortion optimization routine. The paper presents a complexity reduction strategy that aims at reducing the computational load of the Intra coding with a small loss in the compression performance. The proposed algorithm relies on selecting a reduced set of prediction modes according to their probabilities, which are estimated adopting a belief-propagation procedure. Experimental results show that the proposed method permits saving up to 60 % of the coding time required by an exhaustive rate-distortion optimization method with a negligible loss in performance. Moreover, it permits an accurate control of the computational complexity unlike other methods where the computational complexity depends upon the coded sequence.

Fast ITTBC using pattern code on subband segmentation

NASA Astrophysics Data System (ADS)

Koh, Sung S.; Kim, Hanchil; Lee, Kooyoung; Kim, Hongbin; Jeong, Hun; Cho, Gangseok; Kim, Chunghwa

2000-06-01

Iterated Transformation Theory-Based Coding suffers from very high computational complexity in encoding phase. This is due to its exhaustive search. In this paper, our proposed image coding algorithm preprocess an original image to subband segmentation image by wavelet transform before image coding to reduce encoding complexity. A similar block is searched by using the 24 block pattern codes which are coded by the edge information in the image block on the domain pool of the subband segmentation. As a result, numerical data shows that the encoding time of the proposed coding method can be reduced to 98.82% of that of Joaquin's method, while the loss in quality relative to the Jacquin's is about 0.28 dB in PSNR, which is visually negligible.

Code Samples Used for Complexity and Control

NASA Astrophysics Data System (ADS)

Ivancevic, Vladimir G.; Reid, Darryn J.

2015-11-01

The following sections are included: * MathematicaⓇ Code * Generic Chaotic Simulator * Vector Differential Operators * NLS Explorer * 2C++ Code * C++ Lambda Functions for Real Calculus * Accelerometer Data Processor * Simple Predictor-Corrector Integrator * Solving the BVP with the Shooting Method * Linear Hyperbolic PDE Solver * Linear Elliptic PDE Solver * Method of Lines for a Set of the NLS Equations * C# Code * Iterative Equation Solver * Simulated Annealing: A Function Minimum * Simple Nonlinear Dynamics * Nonlinear Pendulum Simulator * Lagrangian Dynamics Simulator * Complex-Valued Crowd Attractor Dynamics * Freeform Fortran Code * Lorenz Attractor Simulator * Complex Lorenz Attractor * Simple SGE Soliton * Complex Signal Presentation * Gaussian Wave Packet * Hermitian Matrices * Euclidean L2-Norm * Vector/Matrix Operations * Plain C-Code: Levenberg-Marquardt Optimizer * Free Basic Code: 2D Crowd Dynamics with 3000 Agents

Standardized Radiation Shield Design Methods: 2005 HZETRN

NASA Technical Reports Server (NTRS)

Wilson, John W.; Tripathi, Ram K.; Badavi, Francis F.; Cucinotta, Francis A.

2006-01-01

Research committed by the Langley Research Center through 1995 resulting in the HZETRN code provides the current basis for shield design methods according to NASA STD-3000 (2005). With this new prominence, the database, basic numerical procedures, and algorithms are being re-examined with new methods of verification and validation being implemented to capture a well defined algorithm for engineering design processes to be used in this early development phase of the Bush initiative. This process provides the methodology to transform the 1995 HZETRN research code into the 2005 HZETRN engineering code to be available for these early design processes. In this paper, we will review the basic derivations including new corrections to the codes to insure improved numerical stability and provide benchmarks for code verification.

Intraoperative Functional Mapping and Monitoring during Glioma Surgery

PubMed Central

SAITO, Taiichi; MURAGAKI, Yoshihiro; MARUYAMA, Takashi; TAMURA, Manabu; NITTA, Masayuki; OKADA, Yoshikazu

2015-01-01

Glioma surgery represents a significant advance with respect to improving resection rates using new surgical techniques, including intraoperative functional mapping, monitoring, and imaging. Functional mapping under awake craniotomy can be used to detect individual eloquent tissues of speech and/or motor functions in order to prevent unexpected deficits and promote extensive resection. In addition, monitoring the patient’s neurological findings during resection is also very useful for maximizing the removal rate and minimizing deficits by alarming that the touched area is close to eloquent regions and fibers. Assessing several types of evoked potentials, including motor evoked potentials (MEPs), sensory evoked potentials (SEPs) and visual evoked potentials (VEPs), is also helpful for performing surgical monitoring in patients under general anesthesia (GA). We herein review the utility of intraoperative mapping and monitoring the assessment of neurological findings, with a particular focus on speech and the motor function, in patients undergoing glioma surgery. PMID:25744346

VEP Responses to Op-Art Stimuli

PubMed Central

O’Hare, Louise; Clarke, Alasdair D. F.; Pollux, Petra M. J.

2015-01-01

Several types of striped patterns have been reported to cause adverse sensations described as visual discomfort. Previous research using op-art-based stimuli has demonstrated that spurious eye movement signals can cause the experience of illusory motion, or shimmering effects, which might be perceived as uncomfortable. Whilst the shimmering effects are one cause of discomfort, another possible contributor to discomfort is excessive neural responses: As striped patterns do not have the statistical redundancy typical of natural images, they are perhaps unable to be encoded efficiently. If this is the case, then this should be seen in the amplitude of the EEG response. This study found that stimuli that were judged to be most comfortable were also those with the lowest EEG amplitude. This provides some support for the idea that excessive neural responses might also contribute to discomfort judgements in normal populations, in stimuli controlled for perceived contrast. PMID:26422207

VEP Responses to Op-Art Stimuli.

PubMed

O'Hare, Louise; Clarke, Alasdair D F; Pollux, Petra M J

2015-01-01

Several types of striped patterns have been reported to cause adverse sensations described as visual discomfort. Previous research using op-art-based stimuli has demonstrated that spurious eye movement signals can cause the experience of illusory motion, or shimmering effects, which might be perceived as uncomfortable. Whilst the shimmering effects are one cause of discomfort, another possible contributor to discomfort is excessive neural responses: As striped patterns do not have the statistical redundancy typical of natural images, they are perhaps unable to be encoded efficiently. If this is the case, then this should be seen in the amplitude of the EEG response. This study found that stimuli that were judged to be most comfortable were also those with the lowest EEG amplitude. This provides some support for the idea that excessive neural responses might also contribute to discomfort judgements in normal populations, in stimuli controlled for perceived contrast.

Event-related potentials to visual, auditory, and bimodal (combined auditory-visual) stimuli.

PubMed

Isoğlu-Alkaç, Ummühan; Kedzior, Karina; Keskindemirci, Gonca; Ermutlu, Numan; Karamursel, Sacit

2007-02-01

The purpose of this study was to investigate the response properties of event related potentials to unimodal and bimodal stimulations. The amplitudes of N1 and P2 were larger during bimodal evoked potentials (BEPs) than auditory evoked potentials (AEPs) in the anterior sites and the amplitudes of P1 were larger during BEPs than VEPs especially at the parieto-occipital locations. Responses to bimodal stimulation had longer latencies than responses to unimodal stimulation. The N1 and P2 components were larger in amplitude and longer in latency during the bimodal paradigm and predominantly occurred at the anterior sites. Therefore, the current bimodal paradigm can be used to investigate the involvement and location of specific neural generators that contribute to higher processing of sensory information. Moreover, this paradigm may be a useful tool to investigate the level of sensory dysfunctions in clinical samples.

Mapping pathological phenotypes in a mouse model of CDKL5 disorder.

PubMed

Amendola, Elena; Zhan, Yang; Mattucci, Camilla; Castroflorio, Enrico; Calcagno, Eleonora; Fuchs, Claudia; Lonetti, Giuseppina; Silingardi, Davide; Vyssotski, Alexei L; Farley, Dominika; Ciani, Elisabetta; Pizzorusso, Tommaso; Giustetto, Maurizio; Gross, Cornelius T

2014-01-01

Mutations in cyclin-dependent kinase-like 5 (CDKL5) cause early-onset epileptic encephalopathy, a neurodevelopmental disorder with similarities to Rett Syndrome. Here we describe the physiological, molecular, and behavioral phenotyping of a Cdkl5 conditional knockout mouse model of CDKL5 disorder. Behavioral analysis of constitutive Cdkl5 knockout mice revealed key features of the human disorder, including limb clasping, hypoactivity, and abnormal eye tracking. Anatomical, physiological, and molecular analysis of the knockout uncovered potential pathological substrates of the disorder, including reduced dendritic arborization of cortical neurons, abnormal electroencephalograph (EEG) responses to convulsant treatment, decreased visual evoked responses (VEPs), and alterations in the Akt/rpS6 signaling pathway. Selective knockout of Cdkl5 in excitatory and inhibitory forebrain neurons allowed us to map the behavioral features of the disorder to separable cell-types. These findings identify physiological and molecular deficits in specific forebrain neuron populations as possible pathological substrates in CDKL5 disorder.

[Clinical feature of ALS with communication disturbance; the possibility to communicate in TLS].

PubMed

Nagao, Masahiro

2013-01-01

In the subsets of amyotrohic lateral sclerosis (ALS), totally-locked in state (TLS) is shown as the result of marked progression of motor neuron degeneration. In TLS, patients are impossible to move any voluntary muscles. As the result, patients with TLS cannot communicate with any augmentative and alternative communication devices(AACD) at present. To find the AACD that enables for TLS to communicate, we examined the clinical character, brain MRI, SPECT and evoked potentials in TLS. Brain MRI showed marked brain atrophy including the brainstem, but the occipital lobe was spared. SPECT and visual evoked potentials (VEP) showed preserved physiological function of the occipital lobe in TLS. The results suggest that neuronal degeneration in TLS is not restricted to motor system, but that the visual pathways are spared. Patients with TLS may be possible to use AACD that utilize the visual pathway.

Description of Panel Method Code ANTARES

NASA Technical Reports Server (NTRS)

Ulbrich, Norbert; George, Mike (Technical Monitor)

2000-01-01

Panel method code ANTARES was developed to compute wall interference corrections in a rectangular wind tunnel. The code uses point doublets to represent blockage effects and line doublets to represent lifting effects of a wind tunnel model. Subsonic compressibility effects are modeled by applying the Prandtl-Glauert transformation. The closed wall, open jet, or perforated wall boundary condition may be assigned to a wall panel centroid. The tunnel walls can be represented by using up to 8000 panels. The accuracy of panel method code ANTARES was successfully investigated by comparing solutions for the closed wall and open jet boundary condition with corresponding Method of Images solutions. Fourier transform solutions of a two-dimensional wind tunnel flow field were used to check the application of the perforated wall boundary condition. Studies showed that the accuracy of panel method code ANTARES can be improved by increasing the total number of wall panels in the circumferential direction. It was also shown that the accuracy decreases with increasing free-stream Mach number of the wind tunnel flow field.

Rate-compatible protograph LDPC code families with linear minimum distance

NASA Technical Reports Server (NTRS)

Divsalar, Dariush (Inventor); Dolinar, Jr., Samuel J (Inventor); Jones, Christopher R. (Inventor)

2012-01-01

Digital communication coding methods are shown, which generate certain types of low-density parity-check (LDPC) codes built from protographs. A first method creates protographs having the linear minimum distance property and comprising at least one variable node with degree less than 3. A second method creates families of protographs of different rates, all having the linear minimum distance property, and structurally identical for all rates except for a rate-dependent designation of certain variable nodes as transmitted or non-transmitted. A third method creates families of protographs of different rates, all having the linear minimum distance property, and structurally identical for all rates except for a rate-dependent designation of the status of certain variable nodes as non-transmitted or set to zero. LDPC codes built from the protographs created by these methods can simultaneously have low error floors and low iterative decoding thresholds, and families of such codes of different rates can be decoded efficiently using a common decoding architecture.

A Very Fast and Angular Momentum Conserving Tree Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marcello, Dominic C., E-mail: dmarce504@gmail.com

There are many methods used to compute the classical gravitational field in astrophysical simulation codes. With the exception of the typically impractical method of direct computation, none ensure conservation of angular momentum to machine precision. Under uniform time-stepping, the Cartesian fast multipole method of Dehnen (also known as the very fast tree code) conserves linear momentum to machine precision. We show that it is possible to modify this method in a way that conserves both angular and linear momenta.

Optical image encryption using QR code and multilevel fingerprints in gyrator transform domains

NASA Astrophysics Data System (ADS)

Wei, Yang; Yan, Aimin; Dong, Jiabin; Hu, Zhijuan; Zhang, Jingtao

2017-11-01

A new concept of GT encryption scheme is proposed in this paper. We present a novel optical image encryption method by using quick response (QR) code and multilevel fingerprint keys in gyrator transform (GT) domains. In this method, an original image is firstly transformed into a QR code, which is placed in the input plane of cascaded GTs. Subsequently, the QR code is encrypted into the cipher-text by using multilevel fingerprint keys. The original image can be obtained easily by reading the high-quality retrieved QR code with hand-held devices. The main parameters used as private keys are GTs' rotation angles and multilevel fingerprints. Biometrics and cryptography are integrated with each other to improve data security. Numerical simulations are performed to demonstrate the validity and feasibility of the proposed encryption scheme. In the future, the method of applying QR codes and fingerprints in GT domains possesses much potential for information security.

Local Laplacian Coding From Theoretical Analysis of Local Coding Schemes for Locally Linear Classification.

PubMed

Pang, Junbiao; Qin, Lei; Zhang, Chunjie; Zhang, Weigang; Huang, Qingming; Yin, Baocai

2015-12-01

Local coordinate coding (LCC) is a framework to approximate a Lipschitz smooth function by combining linear functions into a nonlinear one. For locally linear classification, LCC requires a coding scheme that heavily determines the nonlinear approximation ability, posing two main challenges: 1) the locality making faraway anchors have smaller influences on current data and 2) the flexibility balancing well between the reconstruction of current data and the locality. In this paper, we address the problem from the theoretical analysis of the simplest local coding schemes, i.e., local Gaussian coding and local student coding, and propose local Laplacian coding (LPC) to achieve the locality and the flexibility. We apply LPC into locally linear classifiers to solve diverse classification tasks. The comparable or exceeded performances of state-of-the-art methods demonstrate the effectiveness of the proposed method.

Surface acoustic wave coding for orthogonal frequency coded devices

NASA Technical Reports Server (NTRS)

Malocha, Donald (Inventor); Kozlovski, Nikolai (Inventor)

2011-01-01

Methods and systems for coding SAW OFC devices to mitigate code collisions in a wireless multi-tag system. Each device producing plural stepped frequencies as an OFC signal with a chip offset delay to increase code diversity. A method for assigning a different OCF to each device includes using a matrix based on the number of OFCs needed and the number chips per code, populating each matrix cell with OFC chip, and assigning the codes from the matrix to the devices. The asynchronous passive multi-tag system includes plural surface acoustic wave devices each producing a different OFC signal having the same number of chips and including a chip offset time delay, an algorithm for assigning OFCs to each device, and a transceiver to transmit an interrogation signal and receive OFC signals in response with minimal code collisions during transmission.

Distributed Adaptive Binary Quantization for Fast Nearest Neighbor Search.

PubMed

Xianglong Liu; Zhujin Li; Cheng Deng; Dacheng Tao

2017-11-01

Hashing has been proved an attractive technique for fast nearest neighbor search over big data. Compared with the projection based hashing methods, prototype-based ones own stronger power to generate discriminative binary codes for the data with complex intrinsic structure. However, existing prototype-based methods, such as spherical hashing and K-means hashing, still suffer from the ineffective coding that utilizes the complete binary codes in a hypercube. To address this problem, we propose an adaptive binary quantization (ABQ) method that learns a discriminative hash function with prototypes associated with small unique binary codes. Our alternating optimization adaptively discovers the prototype set and the code set of a varying size in an efficient way, which together robustly approximate the data relations. Our method can be naturally generalized to the product space for long hash codes, and enjoys the fast training linear to the number of the training data. We further devise a distributed framework for the large-scale learning, which can significantly speed up the training of ABQ in the distributed environment that has been widely deployed in many areas nowadays. The extensive experiments on four large-scale (up to 80 million) data sets demonstrate that our method significantly outperforms state-of-the-art hashing methods, with up to 58.84% performance gains relatively.

Rate-compatible protograph LDPC code families with linear minimum distance

NASA Technical Reports Server (NTRS)

Divsalar, Dariush (Inventor); Dolinar, Jr., Samuel J. (Inventor); Jones, Christopher R. (Inventor)

2012-01-01

Digital communication coding methods are shown, which generate certain types of low-density parity-check (LDPC) codes built from protographs. A first method creates protographs having the linear minimum distance property and comprising at least one variable node with degree less than 3. A second method creates families of protographs of different rates, all structurally identical for all rates except for a rate-dependent designation of certain variable nodes as transmitted or non-transmitted. A third method creates families of protographs of different rates, all structurally identical for all rates except for a rate-dependent designation of the status of certain variable nodes as non-transmitted or set to zero. LDPC codes built from the protographs created by these methods can simultaneously have low error floors and low iterative decoding thresholds.

UNIPIC code for simulations of high power microwave devices

NASA Astrophysics Data System (ADS)

Wang, Jianguo; Zhang, Dianhui; Liu, Chunliang; Li, Yongdong; Wang, Yue; Wang, Hongguang; Qiao, Hailiang; Li, Xiaoze

2009-03-01

In this paper, UNIPIC code, a new member in the family of fully electromagnetic particle-in-cell (PIC) codes for simulations of high power microwave (HPM) generation, is introduced. In the UNIPIC code, the electromagnetic fields are updated using the second-order, finite-difference time-domain (FDTD) method, and the particles are moved using the relativistic Newton-Lorentz force equation. The convolutional perfectly matched layer method is used to truncate the open boundaries of HPM devices. To model curved surfaces and avoid the time step reduction in the conformal-path FDTD method, CP weakly conditional-stable FDTD (WCS FDTD) method which combines the WCS FDTD and CP-FDTD methods, is implemented. UNIPIC is two-and-a-half dimensional, is written in the object-oriented C++ language, and can be run on a variety of platforms including WINDOWS, LINUX, and UNIX. Users can use the graphical user's interface to create the geometric structures of the simulated HPM devices, or input the old structures created before. Numerical experiments on some typical HPM devices by using the UNIPIC code are given. The results are compared to those obtained from some well-known PIC codes, which agree well with each other.

New decoding methods of interleaved burst error-correcting codes

NASA Astrophysics Data System (ADS)

Nakano, Y.; Kasahara, M.; Namekawa, T.

1983-04-01

A probabilistic method of single burst error correction, using the syndrome correlation of subcodes which constitute the interleaved code, is presented. This method makes it possible to realize a high capability of burst error correction with less decoding delay. By generalizing this method it is possible to obtain probabilistic method of multiple (m-fold) burst error correction. After estimating the burst error positions using syndrome correlation of subcodes which are interleaved m-fold burst error detecting codes, this second method corrects erasure errors in each subcode and m-fold burst errors. The performance of these two methods is analyzed via computer simulation, and their effectiveness is demonstrated.

GridMan: A grid manipulation system

NASA Technical Reports Server (NTRS)

Eiseman, Peter R.; Wang, Zhu

1992-01-01

GridMan is an interactive grid manipulation system. It operates on grids to produce new grids which conform to user demands. The input grids are not constrained to come from any particular source. They may be generated by algebraic methods, elliptic methods, hyperbolic methods, parabolic methods, or some combination of methods. The methods are included in the various available structured grid generation codes. These codes perform the basic assembly function for the various elements of the initial grid. For block structured grids, the assembly can be quite complex due to a large number of clock corners, edges, and faces for which various connections and orientations must be properly identified. The grid generation codes are distinguished among themselves by their balance between interactive and automatic actions and by their modest variations in control. The basic form of GridMan provides a much more substantial level of grid control and will take its input from any of the structured grid generation codes. The communication link to the outside codes is a data file which contains the grid or section of grid.

Suture Coding: A Novel Educational Guide for Suture Patterns.

PubMed

Gaber, Mohamed; Abdel-Wahed, Ramadan

2015-01-01

This study aims to provide a helpful guide to perform tissue suturing successfully using suture coding-a method for identification of suture patterns and techniques by giving full information about the method of application of each pattern using numbers and symbols. Suture coding helps construct an infrastructure for surgical suture science. It facilitates the easy understanding and learning of suturing techniques and patterns as well as detects the relationship between the different patterns. Guide points are fixed on both edges of the wound to act as a guideline to help practice suture pattern techniques. The arrangement is fixed as 1-3-5-7 and a-c-e-g on one side (whether right or left) and as 2-4-6-8 and b-d-f-h on the other side. Needle placement must start from number 1 or letter "a" and continue to follow the code till the end of the stitching. Some rules are created to be adopted for the application of suture coding. A suture trainer containing guide points that simulate the coding process is used to facilitate the learning of the coding method. (120) Is the code of simple interrupted suture pattern; (ab210) is the code of vertical mattress suture pattern, and (013465)²/3 is the code of Cushing suture pattern. (0A1) Is suggested as a surgical suture language that gives the name and type of the suture pattern used to facilitate its identification. All suture patterns known in the world should start with (0), (A), or (1). There is a relationship between 2 or more surgical patterns according to their codes. It can be concluded that every suture pattern has its own code that helps in the identification of its type, structure, and method of application. Combination between numbers and symbols helps in the understanding of suture techniques easily without complication. There are specific relationships that can be identified between different suture patterns. Coding methods facilitate suture patterns learning process. The use of suture coding can be a good approach to the construction of an infrastructure of surgical suture science and the facilitation of the understanding and learning of suture pattern techniques. Copyright © 2015 Association of Program Directors in Surgery. Published by Elsevier Inc. All rights reserved.

Robust hashing with local models for approximate similarity search.

PubMed

Song, Jingkuan; Yang, Yi; Li, Xuelong; Huang, Zi; Yang, Yang

2014-07-01

Similarity search plays an important role in many applications involving high-dimensional data. Due to the known dimensionality curse, the performance of most existing indexing structures degrades quickly as the feature dimensionality increases. Hashing methods, such as locality sensitive hashing (LSH) and its variants, have been widely used to achieve fast approximate similarity search by trading search quality for efficiency. However, most existing hashing methods make use of randomized algorithms to generate hash codes without considering the specific structural information in the data. In this paper, we propose a novel hashing method, namely, robust hashing with local models (RHLM), which learns a set of robust hash functions to map the high-dimensional data points into binary hash codes by effectively utilizing local structural information. In RHLM, for each individual data point in the training dataset, a local hashing model is learned and used to predict the hash codes of its neighboring data points. The local models from all the data points are globally aligned so that an optimal hash code can be assigned to each data point. After obtaining the hash codes of all the training data points, we design a robust method by employing l2,1 -norm minimization on the loss function to learn effective hash functions, which are then used to map each database point into its hash code. Given a query data point, the search process first maps it into the query hash code by the hash functions and then explores the buckets, which have similar hash codes to the query hash code. Extensive experimental results conducted on real-life datasets show that the proposed RHLM outperforms the state-of-the-art methods in terms of search quality and efficiency.

Anisotropic Resistivity Forward Modelling Using Automatic Generated Higher-order Finite Element Codes

NASA Astrophysics Data System (ADS)

Wang, W.; Liu, J.

2016-12-01

Forward modelling is the general way to obtain responses of geoelectrical structures. Field investigators might find it useful for planning surveys and choosing optimal electrode configurations with respect to their targets. During the past few decades much effort has been put into the development of numerical forward codes, such as integral equation method, finite difference method and finite element method. Nowadays, most researchers prefer the finite element method (FEM) for its flexible meshing scheme, which can handle models with complex geometry. Resistivity Modelling with commercial sofewares such as ANSYS and COMSOL is convenient, but like working with a black box. Modifying the existed codes or developing new codes is somehow a long period. We present a new way to obtain resistivity forward modelling codes quickly, which is based on the commercial sofeware FEPG (Finite element Program Generator). Just with several demanding scripts, FEPG could generate FORTRAN program framework which can easily be altered to adjust our targets. By supposing the electric potential is quadratic in each element of a two-layer model, we obtain quite accurate results with errors less than 1%, while more than 5% errors could appear by linear FE codes. The anisotropic half-space model is supposed to concern vertical distributed fractures. The measured apparent resistivities along the fractures are bigger than results from its orthogonal direction, which are opposite of the true resistivities. Interpretation could be misunderstood if this anisotropic paradox is ignored. The technique we used can obtain scientific codes in a short time. The generated powerful FORTRAN codes could reach accurate results by higher-order assumption and can handle anisotropy to make better interpretations. The method we used could be expand easily to other domain where FE codes are needed.

A Comparison of Fatigue Design Methods

DTIC Science & Technology

2001-04-05

Boiler and Pressure Vessel Code does not...Engineers, "ASME Boiler and Pressure Vessel Code ," ASME, 3 Park Ave., New York, NY 10016-5990. [4] Langer, B. F., "Design of Pressure Vessels Involving... and Pressure Vessel Code [3] presents these methods and has expanded the procedures to other pressure vessels besides nuclear pressure vessels. B.

Hierarchical Recurrent Neural Hashing for Image Retrieval With Hierarchical Convolutional Features.

PubMed

Lu, Xiaoqiang; Chen, Yaxiong; Li, Xuelong

Hashing has been an important and effective technology in image retrieval due to its computational efficiency and fast search speed. The traditional hashing methods usually learn hash functions to obtain binary codes by exploiting hand-crafted features, which cannot optimally represent the information of the sample. Recently, deep learning methods can achieve better performance, since deep learning architectures can learn more effective image representation features. However, these methods only use semantic features to generate hash codes by shallow projection but ignore texture details. In this paper, we proposed a novel hashing method, namely hierarchical recurrent neural hashing (HRNH), to exploit hierarchical recurrent neural network to generate effective hash codes. There are three contributions of this paper. First, a deep hashing method is proposed to extensively exploit both spatial details and semantic information, in which, we leverage hierarchical convolutional features to construct image pyramid representation. Second, our proposed deep network can exploit directly convolutional feature maps as input to preserve the spatial structure of convolutional feature maps. Finally, we propose a new loss function that considers the quantization error of binarizing the continuous embeddings into the discrete binary codes, and simultaneously maintains the semantic similarity and balanceable property of hash codes. Experimental results on four widely used data sets demonstrate that the proposed HRNH can achieve superior performance over other state-of-the-art hashing methods.Hashing has been an important and effective technology in image retrieval due to its computational efficiency and fast search speed. The traditional hashing methods usually learn hash functions to obtain binary codes by exploiting hand-crafted features, which cannot optimally represent the information of the sample. Recently, deep learning methods can achieve better performance, since deep learning architectures can learn more effective image representation features. However, these methods only use semantic features to generate hash codes by shallow projection but ignore texture details. In this paper, we proposed a novel hashing method, namely hierarchical recurrent neural hashing (HRNH), to exploit hierarchical recurrent neural network to generate effective hash codes. There are three contributions of this paper. First, a deep hashing method is proposed to extensively exploit both spatial details and semantic information, in which, we leverage hierarchical convolutional features to construct image pyramid representation. Second, our proposed deep network can exploit directly convolutional feature maps as input to preserve the spatial structure of convolutional feature maps. Finally, we propose a new loss function that considers the quantization error of binarizing the continuous embeddings into the discrete binary codes, and simultaneously maintains the semantic similarity and balanceable property of hash codes. Experimental results on four widely used data sets demonstrate that the proposed HRNH can achieve superior performance over other state-of-the-art hashing methods.

Unique identification code for medical fundus images using blood vessel pattern for tele-ophthalmology applications.

PubMed

Singh, Anushikha; Dutta, Malay Kishore; Sharma, Dilip Kumar

2016-10-01

Identification of fundus images during transmission and storage in database for tele-ophthalmology applications is an important issue in modern era. The proposed work presents a novel accurate method for generation of unique identification code for identification of fundus images for tele-ophthalmology applications and storage in databases. Unlike existing methods of steganography and watermarking, this method does not tamper the medical image as nothing is embedded in this approach and there is no loss of medical information. Strategic combination of unique blood vessel pattern and patient ID is considered for generation of unique identification code for the digital fundus images. Segmented blood vessel pattern near the optic disc is strategically combined with patient ID for generation of a unique identification code for the image. The proposed method of medical image identification is tested on the publically available DRIVE and MESSIDOR database of fundus image and results are encouraging. Experimental results indicate the uniqueness of identification code and lossless recovery of patient identity from unique identification code for integrity verification of fundus images. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Learning Discriminative Binary Codes for Large-scale Cross-modal Retrieval.

PubMed

Xu, Xing; Shen, Fumin; Yang, Yang; Shen, Heng Tao; Li, Xuelong

2017-05-01

Hashing based methods have attracted considerable attention for efficient cross-modal retrieval on large-scale multimedia data. The core problem of cross-modal hashing is how to learn compact binary codes that construct the underlying correlations between heterogeneous features from different modalities. A majority of recent approaches aim at learning hash functions to preserve the pairwise similarities defined by given class labels. However, these methods fail to explicitly explore the discriminative property of class labels during hash function learning. In addition, they usually discard the discrete constraints imposed on the to-be-learned binary codes, and compromise to solve a relaxed problem with quantization to obtain the approximate binary solution. Therefore, the binary codes generated by these methods are suboptimal and less discriminative to different classes. To overcome these drawbacks, we propose a novel cross-modal hashing method, termed discrete cross-modal hashing (DCH), which directly learns discriminative binary codes while retaining the discrete constraints. Specifically, DCH learns modality-specific hash functions for generating unified binary codes, and these binary codes are viewed as representative features for discriminative classification with class labels. An effective discrete optimization algorithm is developed for DCH to jointly learn the modality-specific hash function and the unified binary codes. Extensive experiments on three benchmark data sets highlight the superiority of DCH under various cross-modal scenarios and show its state-of-the-art performance.

The Base 32 Method: An Improved Method for Coding Sibling Constellations.

ERIC Educational Resources Information Center

Perfetti, Lawrence J. Carpenter

1990-01-01

Offers new sibling constellation coding method (Base 32) for genograms using binary and base 32 numbers that saves considerable microcomputer memory. Points out that new method will result in greater ability to store and analyze larger amounts of family data. (Author/CM)

Description and use of LSODE, the Livermore Solver for Ordinary Differential Equations

NASA Technical Reports Server (NTRS)

Radhakrishnan, Krishnan; Hindmarsh, Alan C.

1993-01-01

LSODE, the Livermore Solver for Ordinary Differential Equations, is a package of FORTRAN subroutines designed for the numerical solution of the initial value problem for a system of ordinary differential equations. It is particularly well suited for 'stiff' differential systems, for which the backward differentiation formula method of orders 1 to 5 is provided. The code includes the Adams-Moulton method of orders 1 to 12, so it can be used for nonstiff problems as well. In addition, the user can easily switch methods to increase computational efficiency for problems that change character. For both methods a variety of corrector iteration techniques is included in the code. Also, to minimize computational work, both the step size and method order are varied dynamically. This report presents complete descriptions of the code and integration methods, including their implementation. It also provides a detailed guide to the use of the code, as well as an illustrative example problem.

A novel QC-LDPC code based on the finite field multiplicative group for optical communications

NASA Astrophysics Data System (ADS)

Yuan, Jian-guo; Xu, Liang; Tong, Qing-zhen

2013-09-01

A novel construction method of quasi-cyclic low-density parity-check (QC-LDPC) code is proposed based on the finite field multiplicative group, which has easier construction, more flexible code-length code-rate adjustment and lower encoding/decoding complexity. Moreover, a regular QC-LDPC(5334,4962) code is constructed. The simulation results show that the constructed QC-LDPC(5334,4962) code can gain better error correction performance under the condition of the additive white Gaussian noise (AWGN) channel with iterative decoding sum-product algorithm (SPA). At the bit error rate (BER) of 10-6, the net coding gain (NCG) of the constructed QC-LDPC(5334,4962) code is 1.8 dB, 0.9 dB and 0.2 dB more than that of the classic RS(255,239) code in ITU-T G.975, the LDPC(32640,30592) code in ITU-T G.975.1 and the SCG-LDPC(3969,3720) code constructed by the random method, respectively. So it is more suitable for optical communication systems.

CSTEM User Manual

NASA Technical Reports Server (NTRS)

Hartle, M.; McKnight, R. L.

2000-01-01

This manual is a combination of a user manual, theory manual, and programmer manual. The reader is assumed to have some previous exposure to the finite element method. This manual is written with the idea that the CSTEM (Coupled Structural Thermal Electromagnetic-Computer Code) user needs to have a basic understanding of what the code is actually doing in order to properly use the code. For that reason, the underlying theory and methods used in the code are described to a basic level of detail. The manual gives an overview of the CSTEM code: how the code came into existence, a basic description of what the code does, and the order in which it happens (a flowchart). Appendices provide a listing and very brief description of every file used by the CSTEM code, including the type of file it is, what routine regularly accesses the file, and what routine opens the file, as well as special features included in CSTEM.

Development and evaluation of a Naïve Bayesian model for coding causation of workers' compensation claims.

PubMed

Bertke, S J; Meyers, A R; Wurzelbacher, S J; Bell, J; Lampl, M L; Robins, D

2012-12-01

Tracking and trending rates of injuries and illnesses classified as musculoskeletal disorders caused by ergonomic risk factors such as overexertion and repetitive motion (MSDs) and slips, trips, or falls (STFs) in different industry sectors is of high interest to many researchers. Unfortunately, identifying the cause of injuries and illnesses in large datasets such as workers' compensation systems often requires reading and coding the free form accident text narrative for potentially millions of records. To alleviate the need for manual coding, this paper describes and evaluates a computer auto-coding algorithm that demonstrated the ability to code millions of claims quickly and accurately by learning from a set of previously manually coded claims. The auto-coding program was able to code claims as a musculoskeletal disorders, STF or other with approximately 90% accuracy. The program developed and discussed in this paper provides an accurate and efficient method for identifying the causation of workers' compensation claims as a STF or MSD in a large database based on the unstructured text narrative and resulting injury diagnoses. The program coded thousands of claims in minutes. The method described in this paper can be used by researchers and practitioners to relieve the manual burden of reading and identifying the causation of claims as a STF or MSD. Furthermore, the method can be easily generalized to code/classify other unstructured text narratives. Published by Elsevier Ltd.

43 CFR 11.64 - Injury determination phase-testing and sampling methods.

Code of Federal Regulations, 2012 CFR

2012-10-01

.... In developing these objectives, the availability of information from response actions relating to the...), test cases proving the code works, and any alteration of previously documented code made to adapt the... computer code (if any), test cases proving the code works, and any alteration of previously documented code...

43 CFR 11.64 - Injury determination phase-testing and sampling methods.

Code of Federal Regulations, 2014 CFR

2014-10-01

.... In developing these objectives, the availability of information from response actions relating to the...), test cases proving the code works, and any alteration of previously documented code made to adapt the... computer code (if any), test cases proving the code works, and any alteration of previously documented code...

43 CFR 11.64 - Injury determination phase-testing and sampling methods.

Code of Federal Regulations, 2013 CFR

2013-10-01

.... In developing these objectives, the availability of information from response actions relating to the...), test cases proving the code works, and any alteration of previously documented code made to adapt the... computer code (if any), test cases proving the code works, and any alteration of previously documented code...

Un-collided-flux preconditioning for the first order transport equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rigley, M.; Koebbe, J.; Drumm, C.

2013-07-01

Two codes were tested for the first order neutron transport equation using finite element methods. The un-collided-flux solution is used as a preconditioner for each of these methods. These codes include a least squares finite element method and a discontinuous finite element method. The performance of each code is shown on problems in one and two dimensions. The un-collided-flux preconditioner shows good speedup on each of the given methods. The un-collided-flux preconditioner has been used on the second-order equation, and here we extend those results to the first order equation. (authors)

Psychometric challenges and proposed solutions when scoring facial emotion expression codes.

PubMed

Olderbak, Sally; Hildebrandt, Andrea; Pinkpank, Thomas; Sommer, Werner; Wilhelm, Oliver

2014-12-01

Coding of facial emotion expressions is increasingly performed by automated emotion expression scoring software; however, there is limited discussion on how best to score the resulting codes. We present a discussion of facial emotion expression theories and a review of contemporary emotion expression coding methodology. We highlight methodological challenges pertinent to scoring software-coded facial emotion expression codes and present important psychometric research questions centered on comparing competing scoring procedures of these codes. Then, on the basis of a time series data set collected to assess individual differences in facial emotion expression ability, we derive, apply, and evaluate several statistical procedures, including four scoring methods and four data treatments, to score software-coded emotion expression data. These scoring procedures are illustrated to inform analysis decisions pertaining to the scoring and data treatment of other emotion expression questions and under different experimental circumstances. Overall, we found applying loess smoothing and controlling for baseline facial emotion expression and facial plasticity are recommended methods of data treatment. When scoring facial emotion expression ability, maximum score is preferred. Finally, we discuss the scoring methods and data treatments in the larger context of emotion expression research.

Use of Systematic Methods to Improve Disease Identification in Administrative Data: The Case of Severe Sepsis.

PubMed

Shahraz, Saeid; Lagu, Tara; Ritter, Grant A; Liu, Xiadong; Tompkins, Christopher

2017-03-01

Selection of International Classification of Diseases (ICD)-based coded information for complex conditions such as severe sepsis is a subjective process and the results are sensitive to the codes selected. We use an innovative data exploration method to guide ICD-based case selection for severe sepsis. Using the Nationwide Inpatient Sample, we applied Latent Class Analysis (LCA) to determine if medical coders follow any uniform and sensible coding for observations with severe sepsis. We examined whether ICD-9 codes specific to sepsis (038.xx for septicemia, a subset of 995.9 codes representing Systemic Inflammatory Response syndrome, and 785.52 for septic shock) could all be members of the same latent class. Hospitalizations coded with sepsis-specific codes could be assigned to a latent class of their own. This class constituted 22.8% of all potential sepsis observations. The probability of an observation with any sepsis-specific codes being assigned to the residual class was near 0. The chance of an observation in the residual class having a sepsis-specific code as the principal diagnosis was close to 0. Validity of sepsis class assignment is supported by empirical results, which indicated that in-hospital deaths in the sepsis-specific class were around 4 times as likely as that in the residual class. The conventional methods of defining severe sepsis cases in observational data substantially misclassify sepsis cases. We suggest a methodology that helps reliable selection of ICD codes for conditions that require complex coding.

Probabilistic Structural Analysis Methods (PSAM) for select space propulsion system components

NASA Technical Reports Server (NTRS)

1991-01-01

The fourth year of technical developments on the Numerical Evaluation of Stochastic Structures Under Stress (NESSUS) system for Probabilistic Structural Analysis Methods is summarized. The effort focused on the continued expansion of the Probabilistic Finite Element Method (PFEM) code, the implementation of the Probabilistic Boundary Element Method (PBEM), and the implementation of the Probabilistic Approximate Methods (PAppM) code. The principal focus for the PFEM code is the addition of a multilevel structural dynamics capability. The strategy includes probabilistic loads, treatment of material, geometry uncertainty, and full probabilistic variables. Enhancements are included for the Fast Probability Integration (FPI) algorithms and the addition of Monte Carlo simulation as an alternate. Work on the expert system and boundary element developments continues. The enhanced capability in the computer codes is validated by applications to a turbine blade and to an oxidizer duct.

Compression embedding

DOEpatents

Sandford, M.T. II; Handel, T.G.; Bradley, J.N.

1998-03-10

A method of embedding auxiliary information into the digital representation of host data created by a lossy compression technique is disclosed. The method applies to data compressed with lossy algorithms based on series expansion, quantization to a finite number of symbols, and entropy coding. Lossy compression methods represent the original data as integer indices having redundancy and uncertainty in value by one unit. Indices which are adjacent in value are manipulated to encode auxiliary data. By a substantially reverse process, the embedded auxiliary data can be retrieved easily by an authorized user. Lossy compression methods use loss-less compressions known also as entropy coding, to reduce to the final size the intermediate representation as indices. The efficiency of the compression entropy coding, known also as entropy coding is increased by manipulating the indices at the intermediate stage in the manner taught by the method. 11 figs.

Compression embedding

DOEpatents

Sandford, II, Maxwell T.; Handel, Theodore G.; Bradley, Jonathan N.

1998-01-01

A method of embedding auxiliary information into the digital representation of host data created by a lossy compression technique. The method applies to data compressed with lossy algorithms based on series expansion, quantization to a finite number of symbols, and entropy coding. Lossy compression methods represent the original data as integer indices having redundancy and uncertainty in value by one unit. Indices which are adjacent in value are manipulated to encode auxiliary data. By a substantially reverse process, the embedded auxiliary data can be retrieved easily by an authorized user. Lossy compression methods use loss-less compressions known also as entropy coding, to reduce to the final size the intermediate representation as indices. The efficiency of the compression entropy coding, known also as entropy coding is increased by manipulating the indices at the intermediate stage in the manner taught by the method.

Waveguide-type optical circuits for recognition of optical 8QAM-coded label

NASA Astrophysics Data System (ADS)

Surenkhorol, Tumendemberel; Kishikawa, Hiroki; Goto, Nobuo; Gonchigsumlaa, Khishigjargal

2017-10-01

Optical signal processing is expected to be applied in network nodes. In photonic routers, label recognition is one of the important functions. We have studied different kinds of label recognition methods so far for on-off keying, binary phase-shift keying, quadrature phase-shift keying, and 16 quadrature amplitude modulation-coded labels. We propose a method based on waveguide circuits to recognize an optical eight quadrature amplitude modulation (8QAM)-coded label by simple passive optical signal processing. The recognition of the proposed method is theoretically analyzed and numerically simulated by the finite difference beam propagation method. The noise tolerance is discussed, and bit-error rate against optical signal-to-noise ratio is evaluated. The scalability of the proposed method is also discussed theoretically for two-symbol length 8QAM-coded labels.

Self-assembled software and method of overriding software execution

DOEpatents

Bouchard, Ann M.; Osbourn, Gordon C.

2013-01-08

A computer-implemented software self-assembled system and method for providing an external override and monitoring capability to dynamically self-assembling software containing machines that self-assemble execution sequences and data structures. The method provides an external override machine that can be introduced into a system of self-assembling machines while the machines are executing such that the functionality of the executing software can be changed or paused without stopping the code execution and modifying the existing code. Additionally, a monitoring machine can be introduced without stopping code execution that can monitor specified code execution functions by designated machines and communicate the status to an output device.

A privacy challenge to longitudinal study methods: patient-derived codes.

PubMed

Clay, Fiona J; Ozanne-Smith, Joan; Watson, Wendy; Congiu, Melinda; Fox, Barbara

2006-08-01

Recent changes to privacy legislation in Australia have resulted in more stringent requirements with respect to maintaining the confidentiality of patient health information. We describe a method employed to de-identify health information collected in a longitudinal study using codes. Using a patient-derived code that did not change during the life of the study follow-up resulted in errors in a quarter of the follow-up surveys. This may introduce bias that could compromise the validity of the study. Alternative methods of coding may alleviate some of these issues. However, removal of some of the constraints imposed by interpretations of privacy legislation may be the best way forward.

Coded mask telescopes for X-ray astronomy

NASA Astrophysics Data System (ADS)

Skinner, G. K.; Ponman, T. J.

1987-04-01

The principle of the coded mask techniques are discussed together with the methods of image reconstruction. The coded mask telescopes built at the University of Birmingham, including the SL 1501 coded mask X-ray telescope flown on the Skylark rocket and the Coded Mask Imaging Spectrometer (COMIS) projected for the Soviet space station Mir, are described. A diagram of a coded mask telescope and some designs for coded masks are included.

Multi-level bandwidth efficient block modulation codes

NASA Technical Reports Server (NTRS)

Lin, Shu

1989-01-01

The multilevel technique is investigated for combining block coding and modulation. There are four parts. In the first part, a formulation is presented for signal sets on which modulation codes are to be constructed. Distance measures on a signal set are defined and their properties are developed. In the second part, a general formulation is presented for multilevel modulation codes in terms of component codes with appropriate Euclidean distances. The distance properties, Euclidean weight distribution and linear structure of multilevel modulation codes are investigated. In the third part, several specific methods for constructing multilevel block modulation codes with interdependency among component codes are proposed. Given a multilevel block modulation code C with no interdependency among the binary component codes, the proposed methods give a multilevel block modulation code C which has the same rate as C, a minimum squared Euclidean distance not less than that of code C, a trellis diagram with the same number of states as that of C and a smaller number of nearest neighbor codewords than that of C. In the last part, error performance of block modulation codes is analyzed for an AWGN channel based on soft-decision maximum likelihood decoding. Error probabilities of some specific codes are evaluated based on their Euclidean weight distributions and simulation results.

Adaptive Nodal Transport Methods for Reactor Transient Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas Downar; E. Lewis

2005-08-31

Develop methods for adaptively treating the angular, spatial, and time dependence of the neutron flux in reactor transient analysis. These methods were demonstrated in the DOE transport nodal code VARIANT and the US NRC spatial kinetics code, PARCS.

Integration of a supersonic unsteady aerodynamic code into the NASA FASTEX system

NASA Technical Reports Server (NTRS)

Appa, Kari; Smith, Michael J. C.

1987-01-01

A supersonic unsteady aerodynamic loads prediction method based on the constant pressure method was integrated into the NASA FASTEX system. The updated FASTEX code can be employed for aeroelastic analyses in subsonic and supersonic flow regimes. A brief description of the supersonic constant pressure panel method, as applied to lifting surfaces and body configurations, is followed by a documentation of updates required to incorporate this method in the FASTEX code. Test cases showing correlations of predicted pressure distributions, flutter solutions, and stability derivatives with available data are reported.

Multispectral code excited linear prediction coding and its application in magnetic resonance images.

PubMed

Hu, J H; Wang, Y; Cahill, P T

1997-01-01

This paper reports a multispectral code excited linear prediction (MCELP) method for the compression of multispectral images. Different linear prediction models and adaptation schemes have been compared. The method that uses a forward adaptive autoregressive (AR) model has been proven to achieve a good compromise between performance, complexity, and robustness. This approach is referred to as the MFCELP method. Given a set of multispectral images, the linear predictive coefficients are updated over nonoverlapping three-dimensional (3-D) macroblocks. Each macroblock is further divided into several 3-D micro-blocks, and the best excitation signal for each microblock is determined through an analysis-by-synthesis procedure. The MFCELP method has been applied to multispectral magnetic resonance (MR) images. To satisfy the high quality requirement for medical images, the error between the original image set and the synthesized one is further specified using a vector quantizer. This method has been applied to images from 26 clinical MR neuro studies (20 slices/study, three spectral bands/slice, 256x256 pixels/band, 12 b/pixel). The MFCELP method provides a significant visual improvement over the discrete cosine transform (DCT) based Joint Photographers Expert Group (JPEG) method, the wavelet transform based embedded zero-tree wavelet (EZW) coding method, and the vector tree (VT) coding method, as well as the multispectral segmented autoregressive moving average (MSARMA) method we developed previously.

Optimal patch code design via device characterization

NASA Astrophysics Data System (ADS)

Wu, Wencheng; Dalal, Edul N.

2012-01-01

In many color measurement applications, such as those for color calibration and profiling, "patch code" has been used successfully for job identification and automation to reduce operator errors. A patch code is similar to a barcode, but is intended primarily for use in measurement devices that cannot read barcodes due to limited spatial resolution, such as spectrophotometers. There is an inherent tradeoff between decoding robustness and the number of code levels available for encoding. Previous methods have attempted to address this tradeoff, but those solutions have been sub-optimal. In this paper, we propose a method to design optimal patch codes via device characterization. The tradeoff between decoding robustness and the number of available code levels is optimized in terms of printing and measurement efforts, and decoding robustness against noises from the printing and measurement devices. Effort is drastically reduced relative to previous methods because print-and-measure is minimized through modeling and the use of existing printer profiles. Decoding robustness is improved by distributing the code levels in CIE Lab space rather than in CMYK space.

Multiplexed Detection of Cytokines Based on Dual Bar-Code Strategy and Single-Molecule Counting.

PubMed

Li, Wei; Jiang, Wei; Dai, Shuang; Wang, Lei

2016-02-02

Cytokines play important roles in the immune system and have been regarded as biomarkers. While single cytokine is not specific and accurate enough to meet the strict diagnosis in practice, in this work, we constructed a multiplexed detection method for cytokines based on dual bar-code strategy and single-molecule counting. Taking interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) as model analytes, first, the magnetic nanobead was functionalized with the second antibody and primary bar-code strands, forming a magnetic nanoprobe. Then, through the specific reaction of the second antibody and the antigen that fixed by the primary antibody, sandwich-type immunocomplex was formed on the substrate. Next, the primary bar-code strands as amplification units triggered multibranched hybridization chain reaction (mHCR), producing nicked double-stranded polymers with multiple branched arms, which were served as secondary bar-code strands. Finally, the secondary bar-code strands hybridized with the multimolecule labeled fluorescence probes, generating enhanced fluorescence signals. The numbers of fluorescence dots were counted one by one for quantification with epi-fluorescence microscope. By integrating the primary and secondary bar-code-based amplification strategy and the multimolecule labeled fluorescence probes, this method displayed an excellent sensitivity with the detection limits were both 5 fM. Unlike the typical bar-code assay that the bar-code strands should be released and identified on a microarray, this method is more direct. Moreover, because of the selective immune reaction and the dual bar-code mechanism, the resulting method could detect the two targets simultaneously. Multiple analysis in human serum was also performed, suggesting that our strategy was reliable and had a great potential application in early clinical diagnosis.

The multidimensional Self-Adaptive Grid code, SAGE, version 2

NASA Technical Reports Server (NTRS)

Davies, Carol B.; Venkatapathy, Ethiraj

1995-01-01

This new report on Version 2 of the SAGE code includes all the information in the original publication plus all upgrades and changes to the SAGE code since that time. The two most significant upgrades are the inclusion of a finite-volume option and the ability to adapt and manipulate zonal-matching multiple-grid files. In addition, the original SAGE code has been upgraded to Version 1.1 and includes all options mentioned in this report, with the exception of the multiple grid option and its associated features. Since Version 2 is a larger and more complex code, it is suggested (but not required) that Version 1.1 be used for single-grid applications. This document contains all the information required to run both versions of SAGE. The formulation of the adaption method is described in the first section of this document. The second section is presented in the form of a user guide that explains the input and execution of the code. The third section provides many examples. Successful application of the SAGE code in both two and three dimensions for the solution of various flow problems has proven the code to be robust, portable, and simple to use. Although the basic formulation follows the method of Nakahashi and Deiwert, many modifications have been made to facilitate the use of the self-adaptive grid method for complex grid structures. Modifications to the method and the simple but extensive input options make this a flexible and user-friendly code. The SAGE code can accommodate two-dimensional and three-dimensional, finite-difference and finite-volume, single grid, and zonal-matching multiple grid flow problems.

Toward Developing a Universal Code of Ethics for Adult Educators.

ERIC Educational Resources Information Center

Siegel, Irwin H.

2000-01-01

Presents conflicting viewpoints on a universal code of ethics for adult educators. Suggests objectives of a code (guidance for practice, policymaking direction, common reference point, shared values). Outlines content and methods for implementing a code. (SK)

Code Team Training: Demonstrating Adherence to AHA Guidelines During Pediatric Code Blue Activations.

PubMed

Stewart, Claire; Shoemaker, Jamie; Keller-Smith, Rachel; Edmunds, Katherine; Davis, Andrew; Tegtmeyer, Ken

2017-10-16

Pediatric code blue activations are infrequent events with a high mortality rate despite the best effort of code teams. The best method for training these code teams is debatable; however, it is clear that training is needed to assure adherence to American Heart Association (AHA) Resuscitation Guidelines and to prevent the decay that invariably occurs after Pediatric Advanced Life Support training. The objectives of this project were to train a multidisciplinary, multidepartmental code team and to measure this team's adherence to AHA guidelines during code simulation. Multidisciplinary code team training sessions were held using high-fidelity, in situ simulation. Sessions were held several times per month. Each session was filmed and reviewed for adherence to 5 AHA guidelines: chest compression rate, ventilation rate, chest compression fraction, use of a backboard, and use of a team leader. After the first study period, modifications were made to the code team including implementation of just-in-time training and alteration of the compression team. Thirty-eight sessions were completed, with 31 eligible for video analysis. During the first study period, 1 session adhered to all AHA guidelines. During the second study period, after alteration of the code team and implementation of just-in-time training, no sessions adhered to all AHA guidelines; however, there was an improvement in percentage of sessions adhering to ventilation rate and chest compression rate and an improvement in median ventilation rate. We present a method for training a large code team drawn from multiple hospital departments and a method of assessing code team performance. Despite subjective improvement in code team positioning, communication, and role completion and some improvement in ventilation rate and chest compression rate, we failed to consistently demonstrate improvement in adherence to all guidelines.

Does the 'P300' speller depend on eye gaze?

NASA Astrophysics Data System (ADS)

Brunner, P.; Joshi, S.; Briskin, S.; Wolpaw, J. R.; Bischof, H.; Schalk, G.

2010-10-01

Many people affected by debilitating neuromuscular disorders such as amyotrophic lateral sclerosis, brainstem stroke or spinal cord injury are impaired in their ability to, or are even unable to, communicate. A brain-computer interface (BCI) uses brain signals, rather than muscles, to re-establish communication with the outside world. One particular BCI approach is the so-called 'P300 matrix speller' that was first described by Farwell and Donchin (1988 Electroencephalogr. Clin. Neurophysiol. 70 510-23). It has been widely assumed that this method does not depend on the ability to focus on the desired character, because it was thought that it relies primarily on the P300-evoked potential and minimally, if at all, on other EEG features such as the visual-evoked potential (VEP). This issue is highly relevant for the clinical application of this BCI method, because eye movements may be impaired or lost in the relevant user population. This study investigated the extent to which the performance in a 'P300' speller BCI depends on eye gaze. We evaluated the performance of 17 healthy subjects using a 'P300' matrix speller under two conditions. Under one condition ('letter'), the subjects focused their eye gaze on the intended letter, while under the second condition ('center'), the subjects focused their eye gaze on a fixation cross that was located in the center of the matrix. The results show that the performance of the 'P300' matrix speller in normal subjects depends in considerable measure on gaze direction. They thereby disprove a widespread assumption in BCI research, and suggest that this BCI might function more effectively for people who retain some eye-movement control. The applicability of these findings to people with severe neuromuscular disabilities (particularly in eye-movements) remains to be determined.

Application of Jacobian-free Newton–Krylov method in implicitly solving two-fluid six-equation two-phase flow problems: Implementation, validation and benchmark

DOE PAGES

Zou, Ling; Zhao, Haihua; Zhang, Hongbin

2016-03-09

This work represents a first-of-its-kind successful application to employ advanced numerical methods in solving realistic two-phase flow problems with two-fluid six-equation two-phase flow model. These advanced numerical methods include high-resolution spatial discretization scheme with staggered grids (high-order) fully implicit time integration schemes, and Jacobian-free Newton–Krylov (JFNK) method as the nonlinear solver. The computer code developed in this work has been extensively validated with existing experimental flow boiling data in vertical pipes and rod bundles, which cover wide ranges of experimental conditions, such as pressure, inlet mass flux, wall heat flux and exit void fraction. Additional code-to-code benchmark with the RELAP5-3Dmore » code further verifies the correct code implementation. The combined methods employed in this work exhibit strong robustness in solving two-phase flow problems even when phase appearance (boiling) and realistic discrete flow regimes are considered. Transitional flow regimes used in existing system analysis codes, normally introduced to overcome numerical difficulty, were completely removed in this work. As a result, this in turn provides the possibility to utilize more sophisticated flow regime maps in the future to further improve simulation accuracy.« less

A comparison between implicit and hybrid methods for the calculation of steady and unsteady inlet flows

NASA Technical Reports Server (NTRS)

Coakley, T. J.; Hsieh, T.

1985-01-01

Numerical simulation of steady and unsteady transonic diffuser flows using two different computer codes are discussed and compared with experimental data. The codes solve the Reynolds-averaged, compressible, Navier-Stokes equations using various turbulence models. One of the codes has been applied extensively to diffuser flows and uses the hybrid method of MacCormack. This code is relatively inefficient numerically. The second code, which was developed more recently, is fully implicit and is relatively efficient numerically. Simulations of steady flows using the implicit code are shown to be in good agreement with simulations using the hybrid code. Both simulations are in good agreement with experimental results. Simulations of unsteady flows using the two codes are in good qualitative agreement with each other, although the quantitative agreement is not as good as in the steady flow cases. The implicit code is shown to be eight times faster than the hybrid code for unsteady flow calculations and up to 32 times faster for steady flow calculations. Results of calculations using alternative turbulence models are also discussed.

The historical biogeography of Mammalia

PubMed Central

Springer, Mark S.; Meredith, Robert W.; Janecka, Jan E.; Murphy, William J.

2011-01-01

Palaeobiogeographic reconstructions are underpinned by phylogenies, divergence times and ancestral area reconstructions, which together yield ancestral area chronograms that provide a basis for proposing and testing hypotheses of dispersal and vicariance. Methods for area coding include multi-state coding with a single character, binary coding with multiple characters and string coding. Ancestral reconstruction methods are divided into parsimony versus Bayesian/likelihood approaches. We compared nine methods for reconstructing ancestral areas for placental mammals. Ambiguous reconstructions were a problem for all methods. Important differences resulted from coding areas based on the geographical ranges of extant species versus the geographical provenance of the oldest fossil for each lineage. Africa and South America were reconstructed as the ancestral areas for Afrotheria and Xenarthra, respectively. Most methods reconstructed Eurasia as the ancestral area for Boreoeutheria, Euarchontoglires and Laurasiatheria. The coincidence of molecular dates for the separation of Afrotheria and Xenarthra at approximately 100 Ma with the plate tectonic sundering of Africa and South America hints at the importance of vicariance in the early history of Placentalia. Dispersal has also been important including the origins of Madagascar's endemic mammal fauna. Further studies will benefit from increased taxon sampling and the application of new ancestral area reconstruction methods. PMID:21807730

Multi-level trellis coded modulation and multi-stage decoding

NASA Technical Reports Server (NTRS)

Costello, Daniel J., Jr.; Wu, Jiantian; Lin, Shu

1990-01-01

Several constructions for multi-level trellis codes are presented and many codes with better performance than previously known codes are found. These codes provide a flexible trade-off between coding gain, decoding complexity, and decoding delay. New multi-level trellis coded modulation schemes using generalized set partitioning methods are developed for Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK) signal sets. New rotationally invariant multi-level trellis codes which can be combined with differential encoding to resolve phase ambiguity are presented.

A New Image Encryption Technique Combining Hill Cipher Method, Morse Code and Least Significant Bit Algorithm

NASA Astrophysics Data System (ADS)

Nofriansyah, Dicky; Defit, Sarjon; Nurcahyo, Gunadi W.; Ganefri, G.; Ridwan, R.; Saleh Ahmar, Ansari; Rahim, Robbi

2018-01-01

Cybercrime is one of the most serious threats. Efforts are made to reduce the number of cybercrime is to find new techniques in securing data such as Cryptography, Steganography and Watermarking combination. Cryptography and Steganography is a growing data security science. A combination of Cryptography and Steganography is one effort to improve data integrity. New techniques are used by combining several algorithms, one of which is the incorporation of hill cipher method and Morse code. Morse code is one of the communication codes used in the Scouting field. This code consists of dots and lines. This is a new modern and classic concept to maintain data integrity. The result of the combination of these three methods is expected to generate new algorithms to improve the security of the data, especially images.

A strong shock tube problem calculated by different numerical schemes

NASA Astrophysics Data System (ADS)

Lee, Wen Ho; Clancy, Sean P.

1996-05-01

Calculated results are presented for the solution of a very strong shock tube problem on a coarse mesh using (1) MESA code, (2) UNICORN code, (3) Schulz hydro, and (4) modified TVD scheme. The first two codes are written in Eulerian coordinates, whereas methods (3) and (4) are in Lagrangian coordinates. MESA and UNICORN codes are both of second order and use different monotonic advection method to avoid the Gibbs phenomena. Code (3) uses typical artificial viscosity for inviscid flow, whereas code (4) uses a modified TVD scheme. The test problem is a strong shock tube problem with a pressure ratio of 109 and density ratio of 103 in an ideal gas. For no mass-matching case, Schulz hydro is better than TVD scheme. In the case of mass-matching, there is no difference between them. MESA and UNICORN results are nearly the same. However, the computed positions such as the contact discontinuity (i.e. the material interface) are not as accurate as the Lagrangian methods.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, W.H.; Clancy, S.P.

Calculated results are presented for the solution of a very strong shock tube problem on a coarse mesh using (1) MESA code, (2) UNICORN code, (3) Schulz hydro, and (4) modified TVD scheme. The first two codes are written in Eulerian coordinates, whereas methods (3) and (4) are in Lagrangian coordinates. MESA and UNICORN codes are both of second order and use different monotonic advection method to avoid the Gibbs phenomena. Code (3) uses typical artificial viscosity for inviscid flow, whereas code (4) uses a modified TVD scheme. The test problem is a strong shock tube problem with a pressuremore » ratio of 10{sup 9} and density ratio of 10{sup 3} in an ideal gas. For no mass-matching case, Schulz hydro is better than TVD scheme. In the case of mass-matching, there is no difference between them. MESA and UNICORN results are nearly the same. However, the computed positions such as the contact discontinuity (i.e. the material interface) are not as accurate as the Lagrangian methods. {copyright} {ital 1996 American Institute of Physics.}« less

PCR-free quantitative detection of genetically modified organism from raw materials. An electrochemiluminescence-based bio bar code method.

PubMed

Zhu, Debin; Tang, Yabing; Xing, Da; Chen, Wei R

2008-05-15

A bio bar code assay based on oligonucleotide-modified gold nanoparticles (Au-NPs) provides a PCR-free method for quantitative detection of nucleic acid targets. However, the current bio bar code assay requires lengthy experimental procedures including the preparation and release of bar code DNA probes from the target-nanoparticle complex and immobilization and hybridization of the probes for quantification. Herein, we report a novel PCR-free electrochemiluminescence (ECL)-based bio bar code assay for the quantitative detection of genetically modified organism (GMO) from raw materials. It consists of tris-(2,2'-bipyridyl) ruthenium (TBR)-labeled bar code DNA, nucleic acid hybridization using Au-NPs and biotin-labeled probes, and selective capture of the hybridization complex by streptavidin-coated paramagnetic beads. The detection of target DNA is realized by direct measurement of ECL emission of TBR. It can quantitatively detect target nucleic acids with high speed and sensitivity. This method can be used to quantitatively detect GMO fragments from real GMO products.

Binary image encryption in a joint transform correlator scheme by aid of run-length encoding and QR code

NASA Astrophysics Data System (ADS)

Qin, Yi; Wang, Zhipeng; Wang, Hongjuan; Gong, Qiong

2018-07-01

We propose a binary image encryption method in joint transform correlator (JTC) by aid of the run-length encoding (RLE) and Quick Response (QR) code, which enables lossless retrieval of the primary image. The binary image is encoded with RLE to obtain the highly compressed data, and then the compressed binary image is further scrambled using a chaos-based method. The compressed and scrambled binary image is then transformed into one QR code that will be finally encrypted in JTC. The proposed method successfully, for the first time to our best knowledge, encodes a binary image into a QR code with the identical size of it, and therefore may probe a new way for extending the application of QR code in optical security. Moreover, the preprocessing operations, including RLE, chaos scrambling and the QR code translation, append an additional security level on JTC. We present digital results that confirm our approach.

Rate-Compatible LDPC Codes with Linear Minimum Distance

NASA Technical Reports Server (NTRS)

Divsalar, Dariush; Jones, Christopher; Dolinar, Samuel

2009-01-01

A recently developed method of constructing protograph-based low-density parity-check (LDPC) codes provides for low iterative decoding thresholds and minimum distances proportional to block sizes, and can be used for various code rates. A code constructed by this method can have either fixed input block size or fixed output block size and, in either case, provides rate compatibility. The method comprises two submethods: one for fixed input block size and one for fixed output block size. The first mentioned submethod is useful for applications in which there are requirements for rate-compatible codes that have fixed input block sizes. These are codes in which only the numbers of parity bits are allowed to vary. The fixed-output-blocksize submethod is useful for applications in which framing constraints are imposed on the physical layers of affected communication systems. An example of such a system is one that conforms to one of many new wireless-communication standards that involve the use of orthogonal frequency-division modulation